As I've gotten older, I usually only watch movies once. I don't have any sort of calculation about movies I'll want to see again (and do), it's very much instinctive and based in the moment. Now that I'm older, I tend to have less free time completely to myself, which definitely factors into things: if I'm with my wife or my son, if we watch something, it's gonna be something they want to also see (whether they've seen it or not). So movies that are of interest only to me tend to get marginalized and I'll find time to squeeze them in during odd hours.... which means (generally speaking) I'm more likely to watch something I haven't seen before (and am interested in) than repeat viewing.
If a movie's on TV and I've seen it, I might watch for awhile, depending on my free time. If it's something I really enjoy, in fact, I'll almost always watch a portion on TV, no matter what else is happening. (Case in point: coming across MIDNIGHT RUN the other night).
I still buy Blu-rays of my favorites, partially for the quality, partially for the guarantee of being able to watch whenever I want, and partially for any extras... but at this point that's reserved only for favorites.