The first thing I am wondering about is how this duration is measured. Is it a set time, or does it still depend on the user's willpower even after the initial Great/Noble difference?
If the former, does the mask need to recharge/generate more power for itself? Can it then be activated while half-charged, for a shorter duration? If the latter, does the power simply become harder and harder to control as the duration increases due to your own mental fatigue? Would a user more easily lose focus after a certain amount of time?
Personally, I lean towards the former, since Noble Kanohi are confirmed to have less power total, and so it doesn't make sense to me that they would wear your mind out quicker.
The second thing I wonder about is if every mask has a duration. Now, if the duration limit comes from the user's fatigue forcing them to let go of the power eventually, then it would make sense that every mask has a limit. Tahu had trouble keeping the Vahi in check, for example, but to me that seemed more like the danger of losing control rather than the inability to keep the mask going at all. Losing control of the Vahi could cause a lot of crazy stuff to happen, while losing control of a Huna would likely just make the viewer visible again.
If the duration is inherent to the mask and the energy it uses, then we have the question of how long any mask can be sustained. A Ruru (night vision) would likely draw very little power, since it just allows your eyes to more easily sense light. The Great version can shine like a flashlight when used to its full extent, though, so we must consider that this additional power usage could potentially make the "batteries" (of either the mask or the user's mind) run out quicker.
We also have such things as the Nuva masks, which have greatly expanded capabilities, at least in the sharing aspect. Sharing a power would naturally use some extra energy (and extra mind power), but would it shorten the duration, or is the Nuva masks capable of sustaining themselves just as well even when used at full power?
I don't expect the answers to be readily available (or else I wouldn't ask














