Hello children... Sage Mode limitations?
Well let me sing you a little song about that.
Basically I'll explain the way I always rped it.
Simply put I always rped that I could enter it on a whim just yto get ythat out the way. However, by doing so I could only remain that way for a short period of that post and perhaps slightly into another. It mainly wads used for when the physical hax where needed on a whim. And not really an in battle thing. For example if I was some feet away from an ally and they were being attacked by a stronger faster person I'd use it on a whim to boost Uetto's physical attributes as to get between the two. I tghunk it goes with out saying Uetto's Sage Enhanced speed and strength were top notch, hehehe. Regardless there is a major down side to this and that is how fast it wears off and the power crash sets in.
Now as for gathering energy I always did it lasted x3 of how many post spent gathering. With a max of only being able to go up to 15 post of usage so gathering longer than 5 post is pointless.
As for other means there were clones and my chakra storage scrolls I used as well. I rped both of these allowing 8 rounds of sage mode. This same concept can be used with seal that store natural energy to release it into the user as well. Or one using a curse seal of sorts. And perhaps the Jugo cells.
Other than that I typically merged with my summons in order to achieve the natural energy flow during battle. It was my most common way of using it. Of course there was bno limit to a time span of lasting. It lasted so long as they were merged. But if they could be separated from me than the Sage Mode would instantly break and the chakra crash take over.
Oh I say chakra crash like the crash from using energy drinks. I mean really that is what it is like to me. You use it to get a bust like you would a red bull and then you crash hard when it wears off.