I have repotted while my phals were still in bloom and not lost a flower .. there are some of us here that will repot as soon as they acquire an orchid .. What's best for the plant? Depends on the condition of the orchid ... some need a medium change right away along with a roots inspection and clean-up ...
Again, it's personal preference.
Other than the roots sticking out of the medium, can you observe the roots in the clear pot? How do they look? Are they green and/or white or are they black? Is the medium badly broken down? Does it have a funny odor about it?
You might have a great plant as it is and it may not need to be repotted at this time .. a photo would really help
if possible.
Don't forget to look over the Phalaenopsis Care Sheet OB provides -
http://www.orchidboard.com/Phalaenop...ure-Care-Sheet
You can also check the archives by typing in 'phalaenopsis' in the search option for past threads and check out our Phalaenopsis forum questions directed specifically for phals ( and there are member's photos there, too)
I hope this helps