It is fine. I have been using an "old" canon EOS 1000 for a few years now. But I use an HDMI capture card with magic lantern running on the camera to get a clean HDMI feed.

I use a Canon R6 as a webcam. I noticed it gets reasonably hot after long meetings so I avoid it day to day. It is great, though, for client meetings because they always notice the quality of the image and ask how do I get that nice out of focus background :)

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.

Picture-taking wise DSLR is not any different than e.g. webcam (aside from form factor) - it is just a sensor with electronics to read, process and transmit/store data.

The only thing that differentiates an SLR is the shutter/mirror mechanism, which is mechanical part and lifetime is roughly proportional to a number of "uses".

… exposed to light.

It's still enclosed in a dust-free environment. I'd say unless you shine laser beams directly at the sensor, or point it directly at the sun all day it'll be fine for many years.

Also, some (or most / all?) cameras will close the shutter curtain when disabled. Presumably you would enable the camera only when you need it.