WIth the duels, its very possible that over a 2-4 hours tourney you'd run out of energy, you would have to have energy recharges after each duel or something, and then you enter into the fact that if you're getting free energy recharges, that's going to be the only thing people do. I do love pvp'ing, in fact its almost all I do, but I can't get enough energy cubes to participate in something like that very often.