hi again mary,.. i don't have this orchid but love the black,... it's great to have in collection...
the other may have different opinon about repotting,..
for me,.. best time to repot or not, not gonna risk letting root rotting in old breaking down moss,..
would treat it for fungal and bacteria before giving fresh medium...
as for medium choice,.. maybe the others could give better advice,.. the medium we use here are very different standard,..