My hubby figures Andy needs to wait until the *last* climb to make his move. If he gains time before then Berto will then attack him on the next one, so Andy's best strategy is to cover Berto until the last major climb and hedge his bets on being able to gain some time on that one. And also - that last climb is the Tourmalet - and its a doozy, so saving his energy and just marking Berto in anticipation of that day is probably not such a bad idea.