Hi kotchz,
That really depends on the person and on the “muscle memory” they have developed on their previous mattress and on how different a new mattress is from their old one. While your mattress is probably already broken in from being a floor model … it’s not unusual at all that the adjustment period for a new sleeping surface can be 30 - 90 days (although 90 days would be unusual and closer to 30 would be more typical). Post #2 here may also be helpful.
Phoenix