preferments, times and temps

Preferments are a lot of fun, even for someone like me who bakes with a sourdough starter most of the time. You're correct in thinking that a warm preferment will mature faster than a cool one. If your work space is warm, you can always slow down your preferment or sponge by adding a very small quantity of  salt, about 0.1%, in your sponge and subtracting that weight from the salt when you mix your dough. Jeff Hamelman's book "Bread" has a much more accurate and professional explanation of this step.

Bernard Clayton, in his "Breads of France" wrote his recipes using an entire packet of yeast in his sponges and the reader is advised to let them ferment for 12-14 hours at room temp. Ciril Hitz suggests that a preferment or sponge be made up, rested on the counter for an hour, then put in the fridge overnight. It seems like every popular author has her or his own procedure and since the books keep selling, they can't all be wrong.

Don't fall into the trap of overthinking this stuff. Read your baking books, borrow some from your library, or thumb through one or two at a book store. Try out the different methods and if you like them, go with it. At worst, you'll have to throw away 100g of flour and the 1/2 tsp or so of yeast when you get less than satisfactory results. Having some discipline in executing the procedures for making bread is still important but enjoying what you're doing is just as important.

You don't need to stick to 14 hours - depending on the hydration of the pre-ferment, ambient temperature, amount of yeast used, desired effect etc. , a sponge can be left for a few hours or a few days. The main thing is to use it when it's still active - ideally when  yeast activity is peaking - and before it begins to fall back. If it's tripled in volume, the yeast have almost certainly nearly run out of food and the sponge will soon fall back, so use it at that point. If you leave it too long, the gluten in the sponge will degrade due to enzymatic activity and your finished dough may end up being too soft.

Regarding smell, carbon dioxide is to be expected, as is a very small amount of alcohol. Acetone smells are a bad sign, although I've only ever encountered this in starters.

Neil

Most of my non-sourdough preferment experience is with the biga. Depending on the final product, I usually go between from 44 to 55% hydration, 1% yeast, and 16-20 hours of fermentation at 64-68 degrees F. As with any other part of bread making, there is an infinite number of ways to do it, and some of them go 48+ hours only in the fridge. Perhaps you might try something like that if you want to always work with a stable temperature? Certainly there are breads that would simply not use a biga, but I really love making biga breads. The feel of the dough when you are kneeding/mixing is awesome. If there is no alcohol smell at all, then it isn't ready. My bigas usually slightly more than double before use, but even that can change depending on the product. Once you've made a lot of them, you get a feel for the color, smell, and rise it should have to produce the desired product. I suspect all preferments are similar in that regard.  

If you happen to have a wine cooler, the temp is usually in the 50's and works quite well for slow- fermenting dough (and for keeping some chocolate, too!).