If it's an inclination just to rampage forwards, it's nearly always unnecessary but if it's more a desire to push up and provide some impetus when the play slows down it can be useful, I think he would be encouraged to do the latter, rather than needlessly compromising us. It's one of the things the invincibles did well, knowing when to defend and when to push up, if Vermaelen wasn't just talikng out of his arse about studying the game whilst he was out I suspect he might know how to judge it better this season.