I'm talking years not miles. How many years will a tire last? I had a car (not an acura) sitting for 3 years without being driven parked outside. The tires have a lot of cracking in the sidewalls. The pressure in the tires got down to 15psi. The tires are at least 7 or 8 years old. Should I be concernced?

 

If a tire is not used they begin to dry rot... sitting for that length of time, your tires are showing serious signs of that. If you were to re-inflate that tire, you run the risk of having anything from a slow leak to a tire blow out. I would suggest that you replace those tires before driving any significant distance.

How long it would take for your tire to go bad depends on how much moisture was around where your tire was stored and how much weight (or interal pressure) was placed on the tire.

 

Your main problem would be flatspotting on those tires. They will never roll the same again. Your best bet would be to replace them all.

 

In the future, you're better off to have a car resting on axle stands and the tires deflated to about 20psi so they don't flatspot.

But definitely, those tires are dead. Very unsafe to drive on them (esp at highway speeds).