The Naruto franchise has been going on for long enough now that it should be possible to get some actual numerical values on chakra reserves and how much chakra is regenerated over time. Before I start trying to work this out using various incidents from the anime, I'd like to know if there are any pre-existing "studies" or creator statements regarding this subject?
It really depends on the Shinobi, I mean if they strain their chakra reserves by doing a bunch of exercises, in theory their reserves will grow. Regeneration time depends on the time you rest. If you're asleep you have a faster revival rate, but if you just sit still you'll have a slower revival rate, and if you're active (even if you are not using chakra) you'll have an even slower revival rate.