Being a pot grower (sic) for a a long time, I feel that there are signals you want to watch for.

Drooping leaves and yellowing and lockout are a late sign, but they do tell you it is time.

Another way, is over time you will note how much water the pot/plant needs. I seem to water every other to every 3rd day. Well when that pot uses the same amount of water in 24 hours....that is the signal to repot. IT seems to be a sudden change in my garden