I not sure I like that business model. You have already earned their trust and respect if they are repeat customers as you say. Why would you give them $20, $30, $50 to $100 off next time? I don't understand this. Your goal should be to go above and beyond when it comes to your customers. Make them want to pay more to keep you as the company for pressure washing, not less. Maybe I'm looking at it backwards..... Not saying your way is wrong at all, I'm trying to figure out your goals with these cards, that's all.