In my opinion Rewards programs does not make bad tea good, so if I place an order from you, and I do not like the tea I got, even if you have a very good rewards program I am unlikely to order again. But at the same time the only vendor I order from regularly with a rewards program is O-Cha, and I do not think I have yet to cash my rewards in, I keep telling myself I am saving them to get a very good gyokuro for pennies (or free).
I am not sure if you count this as a rewards program, but I sort of consider it an immediate rewards program. I like vendors that give free samples with an order from them. Its a great way to try new tea's and branch out slightly. It's one of those things where how can you know you can't live without this tea if you've never tried it?