To re-pot or not to re-pot?

[missgroover]

Hi there, I'm not exactly a beginner as have been keeping phaelenopsis for a few years. One of them is a very mature plant (6 yrs +) and is starting to out-grow its pot. It has very healthy leaf growth and a large number of terrestrial roots. When should I repot it, or should I not until it starts to look unhappy?
It recently flowered (14 blooms!!) but has now finished. However another query I have is that it grew half a flower stalk about 18 months ago, this never developed into anything and I have left it on. Should I cut this back to see if it will encourage it to flower?
Generally I leave them well alone as when I have tried to intervene in the past they have taken offence and died on me Any help appreciated.