I won't bash Favre for coming back, it was obviously a great decision, one even I enjoyed.
But I always knew when Warner called it quits (I was expecting last season,) it was done. Kurt Warner has far too many things he enjoys doing, other than playing football. I've always thought of Favre as sitting home, twiddling his thumbs due to boredom, which is why he always comes back - that's not the case for Kurt Warner.