diff --git a/lib/Pyro/ext/remote.py b/lib/Pyro/ext/remote.py
index 5f7a8d6b54e..e446109bac3 100644
--- a/lib/Pyro/ext/remote.py
+++ b/lib/Pyro/ext/remote.py
@@ -104,7 +104,7 @@ def unregister_objects():
 
 def host_ipaddr(interface = None):
 	if sys.platform == "win32":
-		return HostUtil.inst().gethostbyname()
+		return HostUtil.get_inst().gethostbyname()
 
 	cmd = "/sbin/ifconfig"
 	if interface:
@@ -136,7 +136,7 @@ def host_ipaddr(interface = None):
 
 	fd.close()
 
-	return this_host or HostUtil.inst().gethostbyname()
+	return this_host or HostUtil.get_inst().gethostbyname()
 
 def find_nameserver(hostname = None, portnum = None):
 	if hostname and hostname.find('://') > 0:
@@ -152,7 +152,7 @@ def find_nameserver(hostname = None, portnum = None):
 			ns = locator.getNS(host = hostname, port = portnum)
 
 		except (Pyro.core.PyroError, socket.error), x:
-			localhost = HostUtil.inst().gethostbyname('localhost')
+			localhost = HostUtil.get_inst().gethostbyname('localhost')
 			if verbose:
 				print "Error:", x
 				print """
diff --git a/lib/Pyro/naming.py b/lib/Pyro/naming.py
index c52ce27cbc6..876d6430e40 100644
--- a/lib/Pyro/naming.py
+++ b/lib/Pyro/naming.py
@@ -120,7 +120,7 @@ def __sendSysCommand(self,request,host=None,port=None,trace=0,logerrors=1,role=P
 				raise Pyro.errors.PyroError(msg)
 			if bcaddr:
 				try:
-					HostUtil.inst().gethostbyname(bcaddr)
+					HostUtil.get_inst().gethostbyname(bcaddr)
 				except socket.error:
 					msg="invalid broadcast address '%s'" % bcaddr
 					if trace:
diff --git a/lib/Pyro/protocol.py b/lib/Pyro/protocol.py
index 727f07f4fe8..4d2e49980d0 100644
--- a/lib/Pyro/protocol.py
+++ b/lib/Pyro/protocol.py
@@ -58,17 +58,17 @@ class SSLError(Exception): pass
 def getHostname(ip=None):
 	try:
 		if ip:
-			hn,alias, ips = HostUtil.inst().gethostbyaddr(ip)
+			hn,alias, ips = HostUtil.get_inst().gethostbyaddr(ip)
 			return hn
 		else:
-			return HostUtil.inst().gethostname()
+			return HostUtil.get_inst().gethostname()
 	except socket.error:
 		return None
 
 #------ Get IP address (return None on error)
 def getIPAddress(host=None):
 	try:
-		return HostUtil.inst().gethostbyname(host or getHostname())
+		return HostUtil.get_inst().gethostbyname(host or getHostname())
 	except socket.error:
 		return None
 
@@ -1042,7 +1042,7 @@ def __init__(self, port, host='', threaded=_has_threading,prtcol='PYRO'):
 		self.connections = []  # connection threads
 		self.initTLS=lambda tls: None  # default do-nothing func
 		if host:
-			HostUtil.inst().gethostbyname(host)  # validate hostname
+			HostUtil.get_inst().gethostbyname(host)  # validate hostname
 		try:
 			if prtcol=='PYROSSL':
 				try:
diff --git a/lib/Pyro/util.py b/lib/Pyro/util.py
index a7e9922c5d4..96c196c6be4 100644
--- a/lib/Pyro/util.py
+++ b/lib/Pyro/util.py
@@ -52,39 +52,48 @@ def wait(self,timeout=None):
 class HostUtil(object):
     """Wrap and memoize socket.gethost* results."""
 
-    _INST = None
+    EXPIRE = 3600.0  # singleton expires in 1 hour by default
+    _instance = None
 
     @classmethod
-    def inst(cls, reset=False):
-        """Return the singleton of this class."""
-        if cls._INST is None or reset:
-            cls._INST = cls()
-        return cls._INST
+    def get_inst(cls, new=False, expire=None):
+        """Return the singleton instance of this class.
 
-    def __init__(self):
-        self.hostname = None
-        self.hostbyname = {}
-        self.hostbyaddr = {}
+        If "new" is True, create a new singleton instance.
+
+        """
+        if expire is None:
+            expire = cls.EXPIRE
+        if (cls._instance is None or new or
+                time.time() > cls._instance.expire_time):
+            cls._instance = cls(expire)
+        return cls._instance
+
+    def __init__(self, expire):
+        self.expire_time = time.time() + expire
+        self._hostname = None
+        self._hostbyname = {}
+        self._hostbyaddr = {}
 
     def gethostbyaddr(self, addr):
         """Wrap and memoize socket.gethostbyaddr."""
-        if addr not in self.hostbyaddr:
-            self.hostbyaddr[addr] = socket.gethostbyaddr(addr)
-        return self.hostbyaddr[addr]
+        if addr not in self._hostbyaddr:
+            self._hostbyaddr[addr] = socket.gethostbyaddr(addr)
+        return self._hostbyaddr[addr]
 
     def gethostbyname(self, name=None):
         """Wrap and memoize socket.gethostbyname."""
         if name is None:
             name = self.gethostname()
-        if name not in self.hostbyname:
-            self.hostbyname[name] = socket.gethostbyname(name)
-        return self.hostbyname[name]
+        if name not in self._hostbyname:
+            self._hostbyname[name] = socket.gethostbyname(name)
+        return self._hostbyname[name]
 
     def gethostname(self):
         """Wrap and memoize socket.gethostname."""
-        if self.hostname is None:
-            self.hostname = socket.gethostname()
-        return self.hostname
+        if self._hostname is None:
+            self._hostname = socket.gethostname()
+        return self._hostname
 
 
 def getEventObject():
@@ -372,7 +381,7 @@ def getGUID():
 		# For A: should use the machine's MAC ethernet address, but there is no
 		# portable way to get it... use the IP address + 2 bytes process id.
 		try:
-			ip = HostUtil.inst().gethostbyname()
+			ip = HostUtil.get_inst().gethostbyname()
 			networkAddrStr=binascii.hexlify(socket.inet_aton(ip))+"%04x" % os.getpid()
 		except socket.error:
 			# can't get IP address... use another value, like our Python id() and PID
diff --git a/lib/Pyro/wxnsc.py b/lib/Pyro/wxnsc.py
index 197f834a157..6012140e67d 100644
--- a/lib/Pyro/wxnsc.py
+++ b/lib/Pyro/wxnsc.py
@@ -653,7 +653,7 @@ def _setNSData(self):
       Updates the display of current Name Server information.
       """
       try:
-         ns_name, t, ns_ip = HostUtil.inst().gethostbyaddr(self.nsHost)
+         ns_name, t, ns_ip = HostUtil.get_inst().gethostbyaddr(self.nsHost)
          ns_ip = ns_ip[0]
       except:
          ns_name, ns_ip = self.nsHost, ''
diff --git a/lib/cylc/suite_host.py b/lib/cylc/suite_host.py
index 2e48685196a..8a59183dc8a 100644
--- a/lib/cylc/suite_host.py
+++ b/lib/cylc/suite_host.py
@@ -48,25 +48,34 @@
 
 import sys
 import socket
+from time import time
 
 
 class SuiteHostUtil(object):
     """(Suite) host utility."""
 
+    EXPIRE = 3600.0  # singleton expires in 1 hour by default
     _instance = None
 
     @classmethod
-    def get_inst(cls, new=False):
+    def get_inst(cls, new=False, expire=None):
         """Return the singleton instance of this class.
 
-        If "new" is True, create a new singleton instance.
+        "new": if True, create a new singleton instance.
+        "expire":
+            the expire duration in seconds. If None or not specified, the
+            singleton expires after 3600.0 seconds (1 hour). Once expired, the
+            next call to this method will create a new singleton.
 
         """
-        if cls._instance is None or new:
-            cls._instance = cls()
+        if expire is None:
+            expire = cls.EXPIRE
+        if cls._instance is None or new or time() > cls._instance.expire_time:
+            cls._instance = cls(expire)
         return cls._instance
 
-    def __init__(self):
+    def __init__(self, expire):
+        self.expire_time = time() + expire
         self._host_name = None
         self._host_ip_address = None
         self._host_name_pref = None