I think the key word to this question is stamina: Let me explain:
If Boogie and Big Mac were to skate a regular shift all game, on a top line (albeit much more responsibility than an occassional 4th liner) with the bulk of thier concentration on being an integral part of the offense, then I would say that as long as their conditioning and stamina matched Probie, Gillies, etc..I think they are fine, however, if they are gassed, then they will have a problem. Catch one of these behemoths at the end of a hard shift after already playing 10 shifts and it is a different kettle of fish.
Fear always springs from ignorance."
-Ralph Waldo Emerson