I bought a cheap wheel and put a trainer tire on it when I ran out of old regular tires. Many years ago I switched to Kevlar puncture resistant tires, and I typically ride them flat free till threads are showing. Not intentionally, just one day I will notice a bulge and it's because all the tread was gone. Didnt use them on the trainer, so I eventually ran out of old tires.

I have a GP4000 with a fair amount of life in it that I use. It's a gray one and the other is long used up. The colored ones look good on my bike, but then I'm stuck with them so I just saved it for on the trainer.

I haven't switched it out for the few times that I've been able to get out on that bike this year, but it got polished pretty smooth and is pretty entertaining when I have to brake hard right now. It's won't grip much until it wears down a bit, but in two weeks a normal tire goes back on.

Another one who just uses an old cut up tire that still has a little life left. I already buy plenty of crap for this sport.

Yea, my ProTip for the week is to avoid going out for a ride on wet roads using a rear tire that's been on a trainer for a month or so. Either rub the tire with an abrasive pad of some sort or change the tire to something that hasn't been on the trainer.

Recently I went out in a drizzle after pulling my bike off the trainer. The tire I was using had that metallic shine they get, and the second I tried gently turning I almost went down and could hardly touch the rear brake without locking up. Gave it a good scrub with my gloves and let some air out, that helped, but still very sketchy.

My LBS sold me a low cost trainer-wheel/tire combo for $170CAD. I swap it on and off as required without much effort.

For the amount of tire wear that I do in a year, here's what seems to work:

1. Ride one season on a set of tires.
2. When winter comes, keep using those tires on the trainer, and on occasional outside rides when the weather is nice enough.
3. When spring comes again (now), the rear tire will be pretty worn, from both ouside use, and flattened a bit from the trainer. Take off this tire and discard it. Put a new tire on the front of the bike, then put the used front tire (which will have much less wear) on the back.
4. Ride one season on that set.
5. Repeat.

So a tire's life (again, for my amount of riding) is: One season on the front of the bike, then one season on the back of the bike (including winter on the trainer), then trash.... one new tire each spring.