My 2 front wheels are about 5 years old. The one of the front right (passenger) loses air frequently, to the point where I gotta keep adding air every 2 weeks, losing anywhere from 5-15 PSI in between. The 2 back wheels are new from Costco, which cost about $260 I believe. I can purchase another pair for the same price, and have the guarantee stuff, etc etc...but as a starving college student it ain't that easy. Simply put, i'm considering getting two used tires. I've heard both good and bad things and figured i'd ask here for some more 1-on-1 answers, rather than reading up an article on the matter.