I change prices when i do it.
I have a good few thousand cards for rent at the moment. I try not too many changes but twice a season i'll do almost a full change.
Near to the end i'll change prices a few times and raise up everything that's not delegated.
After EOS i'll drop all prices to something standard like 250 DEC/CP see who bites. The markets had fallen off a long way but they do seem to be coming back lately so i'll try to get this back down towards 100 DEC/CP over time.
A lot of changes but low maintenance. It only takes about an hour per season to maintain.