I haven't really played the game at all for several months. It's usually been off and on depending on if I had something to build, many gaps here and there. Every version I typically get on to see what's new, and with v21 I expect to be building more stuff just to try out the lighting.
There will be a point where I fully quit, and it would probably be before the plug was pulled on the game, but the only reason I could think of would be because all interest with the game was lost. But because I still enjoy building with LEGO and games of the sort still, I don't think that will happen any time soon.
Same goes with the forums, I've had a hiatus here and there and returned at some point or another and either stayed for a period or left quickly due to lack of interest. A permanent leave would only occur if I got myself premanently banned (which I try to be quite careful in preventing) or if, like with the game, I had lost total interest.