AR-G and AR-I allow you to specify the number of days since the last sale to designate a customer as inactive o it is up to you to define it.  I suggest using AM-O and AM-P to archive inactive customers and vendors to get them out of the database altogether.

Dear David,
 
Clever work-around! I shall come up with a code for that for use in my system, and put it into play.
 
I think the requested thing though, is to add an "Inactive Customer" tick box in AR-A, the same way there is an "Inactive Vendor" tick box in AP-A, next to the "send 1099" box. That way, when you get notice that someone has folded their tent, or been assimilated by some Borg-like mega company, you can get them out of play quickly, and avoid spending time on them that could better be spent elsewhere.
 
Thanks to everyone who shares such wonderful ideas with all of us! I always learn so much!
Ann

At some point, archiving would be a good idea. But we often get "address forwarding expired" type of issues when the company is still in biz. If they call 2-3 years later to order it's nice to be able to find them in the lookup rather than say "Sorry, we don't have any information on you"...