This may not be a big deal and for all I know it may have been done by design but: I noticed the Endurance spell from the Ranger Class Deck is worded differently from other spells of its kind. The other "Add 3 to a Skill" spells expire at the end of the turn. The Endurance spell ends "At the end of your turn." As written, I assume this would allow the spell to stay in effect for several turns, until the end of the turn of the character who cast the spell, while all other spells of this kind always end after one turn. Anywho, sorry if this came up already. I didn't find mention of it in the FAQ or forums.
Constitution is the only skill that is never used for Combat checks; it comes up when trying to get armour or certain "Fortitude save" effects in encounters, but those aren't common.
So it wouldn't be broken to let Endurance last several turns.
On the other hand, it's inconsistent with other such spells, so it could go either way.
