Re: is sasuke possibly stronger than pein ?
wrong for 2 reasons.
well most of u guys are forgetting that naruto was also tierd and most of his chackra was used up during his training with the toads.
1.Sage mode specifically deals with stamina issues by regenerating chakra at an extremely large rate, this is why naruto looks absolutely exhausted when his sage mode runs out, and then looks absolutely hyperactive ones he activates it again.
Yes it does require your own chakra balancing with natural chakra too, but the whole point of sage mode is to be able to fight your enemy without getting tired.
Better regeneration, less tiredness, more strength etc etc
2.The training on the mountain actually covered a very long time-span, a few manga chapters i believe covered many weeks, maybe month or so.
It wasnt an overnight thing, though admittedly the manga can be seen to show him learning sage mode in that amount of time.