There isn't a general computing forum so posting this here. I've read that powering a computer on and off causes more wear than leaving it on. Is this true and if I have a computer that is idle for days at a time should I power that off?
IMO, don't let worry about component life be a deciding factor. Modern components are robust enough to handle a great many power cycles.
My home PC is 14 years old, still on the original MB, PSU, CPU and GPU, and RAM. HDDs have been replaced over the years.
I leave it on when convenient, I shut it off when convenient. It spent long periods running 24/7 and long periods shut down every night. Though what I do lately is hibernate it (IMO, this is effectively powered down), and I have a 1 hour timeout to auto-hibernate.
I use hibernate, over sleep because you can unplug (or have power failure) while hibernating, and it won't lose data, and you can start right where you left off.