I've used a bunch of DSLRs w/ live preview active for extended periods w/o any issues. It's solid state, so the affect should be negligible assuming you're not directly exposing it to a lot of direct UV light or something like that. For me (used to run a photo automation company), the main wear factor on Canon DSLRs are mirror and shutter actuations (after about 50K-100K actuations, the mirror will tend to detach - this is repairable via CPS), however in preview mode, you aren't going to have any of that mechanical stress.
Sensors getting hot - specially in older cameras - is a well-known problem. Lp doesnt stress the sensor enough (low fps, partially off), but filming video will.
