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Ah the siren song of orchids!
I don't do too well with Phals, and so only have a couple and will let others help with your questions.
Myself, I haven't really had issues arise from repotting most orchids whenever, tho if they aren't new, I do try to do it when there is new growth. New ones, I repot after blooming, if they were in bloom when I got them - or if I am worried about the roots, condition of the plant, I will repot right away.
Repotting the Catt while in bloom is likely to cause the blooms to wither. I agree with Tucker that the roots on yours don't look bad.
I do try to avoid urea based nitrogen fertilizers - mostly because the urea based nitrogen isn't usable at less than 70 degrees, and mine are all usually less than 70 during winter most of the time. I have used - and been happy with - MSU formula, Gubler's, Grow More Orchid (urea free 20-10-10 - blue) - at a rate of 1/2 tsp per gallon water.
Good luck!