When to repot

[Masdyman]

I go on seasons, so I wouldn't repot when the roots have a good chance that they will just sit there and possibly rot, like late Autumn or Winter.

If potting on I don't really worry about the flowers as I don't disturb the roots that much. Obviously if dividing you wouldn't normally do this when in flower anyway.
If I had a orchid that needed dropping on and it was the right time of year then I would drop on, whether in flower or not.
I have yet to lose flowers with this philosophy.