With a new sourdough, you can't assume it will be strong enough for two rises and still have some oven spring left. Some do and some don't, and is it worth the trouble? I like to compare one rise to two, which is what you see below.
This is one batch of dough. It had sponge of about 8 hrs.+, and then mixed to include about a tablespoon of oil and a teaspoon of ground flax seed. The first rise was in the 'fridge overnight and then at room temperature until doubled (about 3 hrs. on the kitchen counter). At that point, one loaf was docked and baked, the rectangular loaf.
The other half of the dough was punched down and shaped into an oval, and had a second rise on the counter, at 73F. After almost doubling, it was then docked and baked. Both loaves were baked for 35 minutes in a 400F oven without steam.
The flavor is only slightly more sour in the oval loaf. The size of the holes in the crumb is the same. The big difference is in the crust. After a single rise, the crust is pale and soft, like most Americans (and my kids) like bread. After two rises, it's darker and crunchy, in a more European style crust.
In this one experiment, I learned 3 useful things: 1) this sourdough is strong enough for a sponge and two rises, 2) a second rise = more crunch, and 3) if I want to make it dramatically more sour or get big bubbles, I'm going to have to work hard at it. And for #3, I probably won't bother because my kids hate real sour with holes the jelly can fall through, and I'm okay with that. It tastes great, and I'll probably only do a second rise if that's more convenient to the schedule of the rest of my life.