Thanks team for your feedback.
I understand that it will not be fair if the companion became "immortal".
But, sometime, when he / she "faint" and I kill all the enemies around "who attacked us". My companion does not "wake up" because there are other enemies around, EVEN WHEN THEY ARE NOT AWARE ABOUT US (sorry for the capital letters, just to clarifies
So, I have to attack them and kill them then my companion awake. No possibility of sneaking after attacking a part of the enemies in dungeon or maze. (sometime, not practical to go back to entrance, get out, from area, then get back and return to continue exploring).
Would be fair to not attack all of them, only the ones that we already engaged with, move to another room and continue the exploration with my companion waked up (and attack other enemies in another rooms that contains quest's items for example).