Nanook,
My approach is a bit different since most of the cattleyas I acquire are in transferred into s/h at some point.
Therefore, I literally remove 100% of the media and 80-90% of the root ball prior to potting them up AND they do just fine!
Given my conditions and watering habits, the "lift and pot bigger" method would result in rot for me.
I don't use bark mix at all for cattleyas.
Regardless of how you choose to repot...you can repot a cattleya hybrid almost anytime of the year and have it recover and do well. As long as it is not in the cold.
If you are wanting to have your temperatures drop down to 55F or so for flowering etc. you should wait a good few months after repotting imo.
If you have a species plant, you
must wait until new roots are presenting or it will die. I learned this the hard way of course