Yes, no problem to enter the lounge as many times as you want. You just have your BP scanned at one of the automated doors at the entrance, and you're free to move around.
I must myself confess that I contribute to the lack of lockers: I often arrive early Morning in Istanbul, get a shower at the lounge, then leave my carry-on in the locker and go to the city for the day or half day, depending on the connection...