I'm sure if you contacted Bob Klee from HTQ, he would be more than happy to go into detail about how they determine if a lead is bad or good. Bob is a very straight shooter.
Aged leads are fine as long as you know you are getting an aged lead. If the consumer isn't interested, they will tell you. Much like the "fresh" leads do.
I do recall that during my Recent use of Home Town Quotes HTQ hometownquotes (search reasons) there were a few people that said that they had gone on line several months ago to get the quote. Luckily HTQ has as one of their credit request reasons "customer stated that he /she requested quote in the past"