@erl it depends mainly on the exposure time, bigger aperture helps to get the faint stars faster. if you had indefinite exposure time, you wouldn't hit much of a limit, but alas.
I normally do projects between 15h and 100h total exposure time with my teensy tiny 2" aperture telescope. You can get an idea of what I see with this Andromeda Galaxy image (total integration 17h) [cropped because Mastodon sucks for large images]