How can I test gloves for long ride comfort?
When testing for something, you wanna make sure you are providing the similar environment for testing as for use.

Exhale some warm moist air on handle-like things, make sure you warm your hands up to the maximum extent by rubbing vigorously, hold them firmly for next 5 or so mins (doesn't matter riding or not).

This'll let you judge 3 things basically:


How they deal with sweat, is the grip impacted!
Is the cushioning sufficient, because we generally don't make such tight grips continuously while riding.
When you remove them and touch their palm side with bare hands, their temperature will tell you about material too. if they're properly ventilated or not.