Aircraft endurance (4-5hrs) > Bladder endurance (3hrs tops!).
I guess the above is partly tongue in cheek, but it isn't that simple.
In the summer, one can go for say 5hrs without a pee. Try that on a freezing cold winter evening!
I fly with the little plastic Tropicana juice bottles (empty of course). Screw tops. Excellent, and go in the bin after a single use.
There is no point in being desperate for a leak, when in the air.