I'm still mourning the loss of my 1993-vintage snow tire a couple weeks ago. I had that one for so long that I'd become emotionally attached to it.
Right now my ol' Corsica has the best set of tires it's had in years. Got some '03 Michelins up front- stored in a shed for years (I bought them a couple years ago from a guy on Craigslist). And some '01 Guardians out back- also stored in a shed for years (I bought them in '02 at a flea market).
I have approximately one full set of used tires left in the garage. By the time I use those up, the tires on the wife's Lumina should be ready to be replaced and passed down to the Corsica.
I know that not everybody can be a cheap [censored] of my caliber, but I've managed to drive this Corsica for the past 8 years/80,000 miles on about $100 worth of tires. Years ago when I was broke and the wife was in grad school, I welded up my own bead-breaker mostly out of scrap metal- it mounts in the receiver hitch of my truck. And I paid $18 on ebay for a bubble-balancer. They've served me well. Those flea market tires that I bought 8 years ago came with a set of wheels that fits the Corsica, so I usually keep at least two used tires set up and ready to bolt on in case I have problems- it happens on occasion.
The biggest problem that I've had over the years with used tires is that they tend to leak around the bead- I guess 'cause the rubber isn't as pliable as it used to be. I've solved that problem with my most recent set of tires that are on the car right now... some of ya'll are gonna hate on me for this, but here's the fix: lube the wheels and beads with GREASE. Just cheap Lithium grease. They slide on easy and seal perfectly. I got the idea from a guy who changed tractor tires for a living- that's how he mounted all of them, and for exactly the same reason (helps them go on easy, and helps the rubber seal). I know that oil and rubber don't necessarily mix well, but I don't think anything will come of it. When I wear out and remove the current tires, I'll see how the rubber held up. I don't expect that it'll cause any problems.