I'm no expert here, but I have a cheap garage sale bike on my trainer. I used to have my tri bike on there, but my LBS guy said that the wear and tear on the bike is tougher than it is on the road. He said that the frame takes a bit more of a beating than outside riding because the trainer is so rigid and doesn't allow for movement. I don't know if he's right or not, but I have a $50 bike on there just in case he's right.
I'm sure it's just fine to have your bike on the trainer for a couple times a week. I don't think it'll hurt it at all. I ride my bike on the trainer 4-5 times a week during the winter, so I'm sure I'm much harder on my bike than you'll be.

Just my little $.02 (for what it's worth)