Once a week is recommended but if you feel the prey isn't filling enough for your snake perhaps either offering two prey once per week or moving up in size of prey might be the answer. Your snake will let you know what works for it.

As far as the fiddling about with prey, sometimes they do just mess about for awhile. One of ours (Rionach) went two weeks where she hit and constricted her prey then oddly felt she had to drag it over to her water dish and dunk it in - repeatedly! Then and only then was it to her snakey satisfaction and promptly (and wetly) snarfed down. Two weeks of this...then she went back to her normal behaviour. Haven't a clue why, snakes are just wierd sometimes LOL.