Cisco routers
4 hours
Cisco switches
5 min
Windows Server 2003 and before
2 min ( 10 min, if the address is reused )
Windows Vista and after
Between 15 sec and 45 sec (random)
Linux box
Various aging time
Switches are able to learn destination MAC addresses from client stations' arp request/query (because switches have longer aging time than client hosts). Those time differences keep them from flooding.
Refferences for Windows box
View the Address Resolution Protocol (ARP) cache
http://technet.microsoft.com/en-us/library/cc786759%28v=WS.10%29.aspx
Description of Address Resolution Protocol (ARP) caching behavior in Windows Vista TCP/IP implementations
http://support.microsoft.com/kb/949589
