Well done! I wonder what media you are using... 2.5" pot and 5 years without repotting, I wouldn't have dared... but it pays off!
I'm lazy when it comes to repotting. Majority of my plants are a few years old in their potting mix. Many need repotting but I just keep delaying. It is my main problem but they all seem to do just fine. The only time I repot my plants is due to lack of space left inside the pot for the roots to grow more. This particular plant has packed the pot with its root. I have a lowii in bloom which has been in the same pot since a few years ago. That plant has grown so many roots that the root ball has raised the plant over the pot by a couple of inches!
Back to your question.
This plant is potted in the mix of small orchiata and lava rock (or lava rock & hydroton). I use the same mix on pretty much all my orchids which is a mixutre of Orchiata, perlite, hydroton. For some paphs, I would topdress with some sphagnum moss. I grow indoor and the air is very dry especially during the winter into spring.
When I bought this plant, it did not have a lot of roots, so I changed the ratio of the ingredients where the inorganic portion was higher than the organic. That probably helps with the potting mix longevity also. However, I usually mix in about half organic and half inorganic. Sometimes more organic. It all depends.
Also, I wait until the potting mix dries out completely before watering again. Plus, the air is much drier than some professional setting. I also fertilize lightly and infrequently. So, I think these might also contribute to slower breakdown of the organic ingredients.
