With indoor trainer season coming up, I'm thinking about getting an extra wheel to use on the trainer. Is the savings in wear on the rear tire and rim worth the expense and hassle? Also, would I need to use the exact same model cassette that I use with my regular wheel, or could I use a different (cheap) cassette?
I ride on the road in the winter when possible, so I would want to be able to swap the trainer wheel in and out easily. That is, I wouldn't want to just put a trainer tire on my regular wheel for the winter.
I have a similar setup for this winter. A trainer will shred your tire, but doesn't actually hurt your wheel. The real benefit of having a dedicated wheel is the luxury of not having to change tires. And you should be able to use a cheap cassette. Better to use a new cheap cassette than a nice but worn one.
Buying a dedicated trainer wheel/tire/cassette is strictly a $$ vs. hassle question.
You don't need a trainer tire. They reduce noise and heat, in theory, but I don't notice a difference. You just need to adjust the tension properly and you won't experience that much shredding. If you're riding in the winter, swapping out your current tires for a more durable set may be a worthwhile thing to do anyway.
If you buy a rig, cheap cassette is fine. You should be able to get a cheap wheel/tire/cassette for a couple of hundred. Or you could use an old t-shirt to wipe your tire off before you put it on the trainer.