Provider standard ARP Timeout?

[Jay Nakamura <zeusdadog () gmail com>]

Cisco default ARP timeout is 4 hours.  Do anyone change that to
something shorter in a provider environment for customer with Ethernet
connectivity?  What is a good value to set it to?

Are there any impacts for lowering the timeout?  Other than higher CPU
util for doing ARP a lot more on the router?