I think the main criterium should be whether the BM has proven to be trustworthy. 
There are a few guys that contribute a lot but because they stir the pot or can be a bit confrontational the advanced status is withheld. 
As Beetleguese said : there is not a whole lot really going on in advanced. so as long as valued members aren't sharing information they shouldn't why not bump them up? 
Just my opinion.