I have tried discounts in the past, like Amy I have limits and plenty of regular clients. Some regulars get overruns and have lots of requests, some like a little contact between bookings, some are unreliable so to then offer discount only seems as if I'd be selling myself short. Some new clients have zero requests, zero faffing, turn up, pay the correct fee (had just as many payment mistakes with regulars as new clients), leave within or exactly on time. New clients have to pay a deposit which can be a good equaliser.
I do have a couple of regulars on a very old rate, one really does push it regards time and bumbling things, the other is absolutely fine very happy to offer him the lower rate.