Most parts of the computer are solid state, and they encounter some thermal stresses from being turned on and off (processor endures most thermal stress because it gets hottest), but this stress is negligible. When was the last time you heard of a processor suddenly dying from normal use? Never, because as long as they are used reasonably, you can almost expect them to last a lifetime.
The only thing I would maybe be concerned about is the hard drive because it is a mechanical device. Each time you start and stop the drive, this places stress on the head. I believe the head actually lands on the drive when it turns off because the air cushion from the spinning platters isnt there anymore. Comparing two general WD drives, the 3.5 inch is only rated for 50k on/off cycles, whereas the 2.5 notebook drive is rated at 600k, so the notebook drive might be better for you. Theoretically, with the notebook drive, you can turn the computer on and off 100 times a day and it would take you 16 years to ruin it.