How to know when to repot?

[greenpassion]

I am more familiar with orchids in S/H, so this business of re-potting a phal that's been in moss and or bark is sketchy to me. Do they always have to be repotted every year? I've grown bananas and many other tropicals - and it's easy to tell when they need it. They become nearly root bound. But am I supposed to just repot every year, even when the plant doesn't look root bound? My phals in S/H all have lots of air roots as well as tons of roots growing down into the PA. My orchids in moss/bark don't look root bound, nor do they have any significant air roots above the potting medium.