And then disappears again, its nothing to become obsessed with. I've seen plenty of warriors using Endure Pain before a battle even starts like they think it gives you +250 health but doesn't take it away again when it runs out. Its only useful for keeping you alive when your almost dead.
High HP is good to prevent you from getting spiked to death, it gives you a few extra seconds to heal yourself. It may be a little useful in PvP, but in PvE, armor and stances are much better than extra HP.
