Spritzhenry has done at least one blog on this but I have to say I find it rare to need to repot them. If you do make sure you use the clear orchid pot and orchid compost.

The only thing that I heard that maybe nessesary is to change the compost for fresh after a few years as it may break down and not allow free drainage

Yes I change mine every couple of years and use good orchid bark .

And use 2 feeds Vitax Orchid in bloom feed and Vitax in growth feed.

So Enjoy all my Orchids.

My rule of thumb is to repot when there are more roots outside the pot, than in.

In sphag moss I do them every couple of years. This is the blog for this process...........

http://www.growsonyou.com/meanie/blog/17827-re-potting-a-phalaenopsis-in-sphag-moss

To repot using orchid compost the process is much the same, but more fiddly packing the rootball.