truth be told, they're not even gonna play that long between breaks. sometimes coaches will change lines after as few as 20 seconds if they're trying to keep their skaters fresh. a normal shift will last around 45 seconds to a minute, which sounds short, but given the bursts of speed, the physicality of the game, and the overall stress you put your body through in those short times... it's plenty lengthy. a good forward will typically get around 20 minutes per game and a good defenseman about 23+ minutes so you have to take into consideration how often they're on and off the ice. that's typical of the NHL and most other leagues.