Thermal cycling causes stress/ fatigue on all electrical components, devices, fixtures, etc. It's what wears them out; kills them, brings them to the end of their life. If you turn on an incandescent light bulb for one minute every five minutes, it likely won't last a month. But if you turn it on and leave it on forever, it may last ten or more years. Same holds true with everything in your pc. Repetitive thermal cycling will shorten the life relative to just leaving it on. As for laptops in particular, there have been instances of the battery charger making the battery too hot and causing a fire, but that has been corrected. If you are constantly turning computers on and off, that may be why you have been through 15 of them. (no offense intended here). The computer I'm typing on right now is an old (7-8 years?) P-IV Dell which sometimes goes 6 months without being turned off. I run Autocad, Photoshop and other intensive applications regulalry and concurrently on this dino.
Check the web. There are utilities which will start your computer at a specified time. Also, most computers will have an "auto start" alternative in the BIOS. Once booted, if desired, you can have Windows Scheduled Tasks run a "mouse macro*" and have it automatically load your apps plus make selections for your setup.. * usually requires the macro be saved in a ".exe" file.... not all do.
Some folks just have bad luck with computers. I have some servers that have run for over ten years now without shutdown. They're PII's. I have a Compaq Pesario laptop and two Dell latitudes that have been running for over four years now since their last powerdown. I just accessed a first generation Pentium that's in my parents basement to send them a fax (they still have WordPerfect and windows 98 on that one). It's been running well over seven years now without a shutdown. They have a Novell server in there also that handles their old files and data. It's Novell Version 3.0 and they are fearful of shutting that puppy down because they don't remember the password. It's been running since, uh, ....