Same here, about a week. Though I've had some eat all the way up to night before molting. And I've had some refuse a meal and molt days later. You don't know exactly when premolt started especially if you feed once a week like some of us do.
Why not give it more substrate and let it make it's cave, one that you started, next to the glass. then you'll be able to time the three to four weeks that it will take to go from premolt to molted and out.
Mine takes almost a month everytime so far to complete the cycle. had it since it was .75" and after this molt, it should be close to 2.25" (leg span). Keep records of the molts and you'll wind up with better ideas of how long they will take.