My wife's does not fly much without it being a free ticket from my accounts, but wen her AA miles were close to expiration, I signed her up for online statements and also the AOL/AAdvantage, getting 1000 and 500 miles respectively to keep the miles around longer.

I also have a HHonors card and when my account was inactive for almost a year, I got a warning that I needed to either have activity within a year or pay a fee to keep my account from closing. That is a pretty strict expiration policy by today's standards - requiring activity within 1 year to keep them.