Bloke goes to his GP with his wife, complaining that she is oversexed and wants to be shagged all the time, and he just doesn't know what to do to satisfy her.
GP says, 'OK, just watch this' and he bends the wife over his desk and pulls her dress up, then starts shagging her. 10 minutes pass, then 20 and after half an hour she is a trembling wreck.
'Now' says the GP 'she needs that 3 times a week, ok?'
That's fine says the bloke, I can bring her Monday, Wednesday and Friday if that suits you....'