Personally I have to work out whether it is going to benefit me by adding on, things like how deep are we in the Tournament, am I going to make the money, but there is one surprising thing, some players cannot afford the add on because they overstretch themselves or they have made the Tournament through a free-roll so don't have the funds.
In one game I was actually chip leader by the break and in order to guarantee being there after the break had to add on regardless of the fact, also I was the bubble boy in another game and because I added on at the break, I finished in the money as there were some that didn't add on.
I think the right answer would be, Can you afford not to Add on, will it make a difference?