[QUOTprecision,age;15211285]Fact Sakura reserves are the smallest in the village,thats why it took Her 3 years to fill Her seal and at that rate it be a noter 3 years to fill up again if She empty it. It takes Tsunade a few days of eating,sleeping and drinking to get back in health. Tsunade was in a coma for days maybe a month. Sakura would be in a coma for years.[/QUOTE]
It took her three years to master the technique, the technique involves extreme chakra precision at one spot, and only she and Tsunade can employ it in battle.
And about the time it took her to master it, we'll atleast she managed to master it when others like Shizune have failed.
Sakura's high level chakra control and more efficient use of the seal will ensure she can refill it in a reasonable amount of time.
But at the moment that's irrelevant, the question will she have to use it against the Madara confrontation
She hasn't even used it to its full potential so far,