I've seen coupons with terms that the car must be reserved through a travel agent or that the coupon must be printed and left at check-in. This one, for example, has both those conditions:
http://www.avis.com/car-rental/html/...lyupgrade.html
MUTA003 - $15 off five-day rental + one-class upgrade, so it's quite good and I'd like to use it. (Funnily enough, "muta" means bribe in Swedish.)

Do Avis agents usually bother about these conditions?

If so, for the travel agent condition, would it be enough to enter an IATA number when I make the reservation at Avis.com? I asked the travel agent at work and she didn't know what else to do.

Regarding bringing a paper coupon, I have a (very old) paper coupon that has expired according to the terms, but I tried using it at Avis.com and it was accepted. I just don't want to be in a position that the agent refuses the coupon because I have an old date on the paper.

Does Avis renew old coupon codes every once in a while or could this be a recycled coupon code that has completely different terms now?