How tightly should an orchid fit in it's container?

[WhiteRabbit]

I don't usually pot up a size unless the plant is busting out of it's pot (new growth growing over the side, or new growth smushed up tightly against the pot), or if I am repotting to give the plant fresh media, and either roots and some media won't fit back into the same size, or there's not room for a year or two's new growth.
I'm always in favor of smaller pots as much as possible (and confess to being one of those who's orchids sometimes appear to be in ridiculously small pots - but that's usually after they have been in those pots a year or two).