Well
@stepside
It all depends. Number of plants, how hungry they are evaporation. ...yada yada.
Biut 10 days til its to low for me to scoop out easily. So I top off. This weekend I'll give them fresh food/nutes. Then ten days or so, depebding on my laziness, I'll top it off. But that will be the last top off. By then the girls shiuld be looking like its Autumn and they'll start super model diet. So you have about 3-4 weeks before trim. That's what I'm guessing right now.