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.).