Leaving dough out too long will overproof it. Leaving it out not long enough will not rise enough, or, in the case of sourdough, not develop that sour taste people are looking for.
Your first loaf is unlikely to come out great, if your starter is not matured yet - because the yeast/bacteria ratio in it is unlikely to be optimal.
The normal recipe is to leave 24 hours the dough in fridge and it says that you can leave it for 48 or even 96 hours :)