Lego is not a normal, profit-seeking corporation, for better or for worse. It would be run very differently if it were publicly traded and vulnerable to the power plays of activist investors. If a set truly sells terribly, like 10227, Lego will end production early. I don't think that was the case with town hall or R2. The latter was essentially due for retirement, next in line after SSD. TH is an interesting case, and I have no idea what they were thinking. But if Lego bases lifespans on sales, then we are to believe that The Zombies was the worst selling Monster Fighters set, The Burrow was the worst selling Harry Potter set of the last run, and assorted other dubious ideas.