Good old stretch and fold

Typically, stretch and folds are made throughout the proof. So, for example, if you have a recipe that calls for a 5 hour proof you might perform a stretch and fold each hour during that process. Some folks like to perform most of their stretch and folds during the early part of the bulk fermentation and then leave their dough undisturbed for the final 2+ hours or so. 

It can be a fairly personalized process. People usually settle into a folding schedule that works best for them.

Also keep in mind that when a recipe specifies a 5 hour proof, or "X" hour proof, that's just a guideline. The rate at which dough proofs is very dependent upon the prevailing temperature conditions and many other factors. So it might have taken the author 5 hours to proof that bread under one set of conditions; and it might take you 4 hours, or 6 hours, or whatever under your conditions.

What's important is to learn to judge the degree of proof so you can manage proof time in a manner that works for you and the conditions in which you're baking. And that's a skill that'll come in time. 

Cheers!

Trevor

Also, different doughs require a different amount of stretching and folding. Some are good with just one (this is usually a dough with lower hydration, like 65%), where others (usually higher hydration around 75% - 80%) will require more to develop a strong structure. It also depends how much whole grain is in the dough. As Trevor says, learn to feel and see when the dough is 'ready'. It should hold itself in a ball shape with a bit of surface tension after a stretch and fold or two, and then relax into a 'puddle' after a while. Once relaxed, that's when you can stretch and fold it again.

Read the dough as well as the recipe!