Once invigoration has been unlocked, there is less of a limit to the amount of adventuring you can do in one day. Guidance also saves precious energy.
However, I feel that the punishment for not having enough energy is adequate. Died in a fight last night due to not being able to use combat abilities or run away, both because of running low on energy.
Invigoration causes stress, so though it prolongs the time spent exploring, you have to be aware of that.
qilongfei, if you are exploring, fighting every encounter you come across, the stress from combat might well be what sends you home rather than low energy. But if you are skipping encounters (eg innocent bystanders), the relative stress cost of casting invigorate is acceptable. As you're not stacking the stress caused by casting on top of stress caused by combat. So once this spell is in play, the system seems more balanced.
(If and when the players magic affinity gets high enough, the stress caused by this spell can be negated, or reversed, reducing the targets stress! But as you have to be a high leveled and magic focused character to pull this off, it doesn't feel game breaking. More like a perk for being an awesome mage haha.
func invigorateeffect(): person.stress += rand_range(25,35)-globals.player.smaf*4)