Levain not rising as it should
So, I'm still trying to figure out sourdough/levain breads. I've had/maintained an active (125% hydration) culture for some time now (several months?), but I don't have the time to use it very often so I keep it in the fridge most of the time.
When I am going to use it, I generally take it out at least a couple of days ahead of time and feed it every twelve hours. It shows all the signs of being ripe and ready to use (lots of bubbles bursting at the surface, acidic smell, etc.).
I have tried a couple of the recipes from Hammelman's Bread book (Sourdough Seed Bread twice, Whole Wheat Levain once), but each time, when it comes to the end of the bulk fermentation, my dough has no gas bubbles in it whatsoever and has not risen or expanded.
Each time, however, I have left the dough out at room temp, as is, overnight (after the 2.5 hr. bulk fermentation period-so about an extra 8 hrs...) and found that in the morning there was at least a little bit of gas formation in the dough, although still not much.
I am at a loss as to what I am doing wrong.
*Generally every time, my starter seems to be more active than the recipe is calling for. It's ripe before the 12 hours that Hammelman calls for, usually at least by about 8 hours.
*Maybe it's expending all of its energy too quickly, and has nothing left for the final dough?
Any advice, comments, suggestions that anybody has are welcome.