$64 question. At most any shoreside bar around the world, when you buy enough drinks and tip the bartender appropriately, or perhaps generously, it is customary for a periodic buy back, i.e. a free drink. I always tip at the ship bars on Cunard and while I seem to get cheerful service and a lot of attention, I don't think I've ever gotten a free drink. I have gotten a "top off", but somehow that's not the same. Any thoughts or comments?