It's kind of apples to oranges. If you have some mission critical need that would require an extra fifteen minutes or so of operating time, then top the batteries off. Or just carry a spare set, if you are standing a post it would be easy to slip 3 batteries into any kind of duty bag (or pouch).
Personally, I think it's a waste of time trying to squeeze a few extra minutes out of batteries when easily obtained mobile charging solutions are available, and not expensive.
Personally, I think it's a waste of time trying to squeeze a few extra minutes out of batteries when easily obtained mobile charging solutions are available, and not expensive.