Snakes will shed at regular intervals throughout their lives. The frequency decreases with age.
Personally I don't pay any attention to humidity. My waterbowls hold a fair amount of water and this seems to provide all the humidity required as the water evaporates naturally.
If a snake has shedding problems I either use the pillow technique (place snake in damp pillowcase in the warm part of the tank) or a wetbox (plastic box with a lukewarm damp towel.