Hi Brambles, welcome to the OB.
You'll be happy to know that your phal looks healthy and, and those blooms are beautiful.
To repot or not to repot? usually you'd repot when the media the orchid is potted in gets soggy and decomposed. I see a little bit algae on your bark, so you might as well. Phals tend to take repotting less hard even when in bloom.
As for the roots, well, if they are dried up on the top of the media, cut back, the same as if they are rotten beneath the media, you'll spot them easily because they'll be black-ish and mushy.
The following is a very helpful link to repotting phals.
Easy Orchids - Re Potting A Phalaenopsis
Just another thing, whether you pin it on luck or not, you have done good with your orchid. Most of us beginners tend to overwater and rot the orchids, worry not, they will handle lack of water better than they can handle excess of.
You can establish a watering schedule once you repot. That will be up to your growing conditions (temperature, humidity, light, etc)
I can tell you there's nothing apparently wrong with you phal from where I see.
keep us posted!