I have been donating blood for 25 years now - two or three times a year, as they normally only take a donation at least 16 weeks after the previous one.
The National Blood Service has, it seems, decided to reward "frequent flyers", as I have received a letter, congratulating me on giving blood 3 times in 12 months (not the first time, but the first time it has been commented on), and offering me a "a special cemmemorative slate coaster ... as a small token of our appreciation"
I feel quite touched! ;-)
(and I am NOT being cynical)