Sure, you could pre-cast Endurance ... if you knew who was going to go down. Or if you had one for each member of the party. ("Now, Merlin! You know you shouldn't give out Endurance spells unless you have one for everybody. You Dispel that right now!) And if you knew that the dangerous encounter wouldn't happen before the duration expired.
Best, I think, to hold that slot until someone needs it. Although it would be reasonable to bop the barbarian with it when he's down to 8 hit points out of 112. Especially if he's raging and gets the Con bonus ... Hey, do those stack?
Best, I think, to hold that slot until someone needs it. Although it would be reasonable to bop the barbarian with it when he's down to 8 hit points out of 112. Especially if he's raging and gets the Con bonus ... Hey, do those stack?
