It is no different than some of the marketing I have seen; end of year studio sale, open house and sale, Christmas open house, the list goes on. A coupon worth actual dollars off usually works better, as in $10.00 off your next painting purchase. You print on the coupon how you want the customer to redeem, giving it an expiration date and your email address. There are many ways to encourage future sales, refer a friend and get a discount, buy one get one half off, Collectors Club, go into any retail store and see how they market. Will it work in the art world? Who knows. As far as being annoyed about getting a coupon, they simply pitch it if they don't want it. If you are sending emails to your collectors it might be used during times when sales are slow to generate some interest. I don't think coupons are any different than the barrage of social media marketing artists are expected to do. In some way, since you already know the customer from a prior purchase it is a lot more personal. Just some thoughts. Interesting conversation Sunny, thanks for bringing it up.