It all depends on what type/species of orchid you are repotting. Some can be potted right after it flowers and others are more tempermental. Send pics and we'll give you some good info.
Phalaenopsis grow continuously during the year. Most experts recommend repotting them after the plant finishes blooming and the flowers drop off. That's worked well for me.
Many cattleyas don't grow during the winter. Most growers say to repot catts when you first see new roots starting to grow. That's a good rule of thumb especially for bifoliate cattleyas. Never repot a bifoliate cattleya until you see new roots. I've found that unifoliate cattleyas can be repotted in the spring even if they haven't started growing yet because they soon will start. Springtime is actually a good time to repot most orchids.