My book says to stop wrapping when they can roll onto their tummy, so that they can use their arms to lift themselves etc if they get their little faces in the bedding etc for safety reasons. If he uses this as his sleeping cue though you might want to do it gradually, wrap him with one arm out for a few sleeps then the other then just under his arms then off altogether, maybe with a sleeping bag instead if you don't use a sheet? HTH.