I definitely (sp?) do not have the track record of say I don't know,
Greg Raymer, but if you poke around on 2+2, he has a few nice posts about when and why to addon.
My advice, is basically what he said (so technically it's his advice), and I am going to have to agree with the WSOP
If I ever post some advice that is wrong (and chances are pretty good that more than half the things I post are/will be wrong---or else I would be playing for a living), and a top Pro contradicts my advice, I will have to admit that I am wrong and they are right.
In this case, I'm going to stick with Raymer's advice, ALWAYS add-on.