This is exactly why I've stopped buying movies. The argument is that if you want to watch it again then you'll have to rent it again, and after a couple times you would have saved money by buying it. That's not true if there's a decent chance buying it still wouldn't let you watch it again in a couple years.
I've just accepted that I'll only be able to watch things once and that's fine, I have much better things to do with my life than watch movies (like starting arguments on HN.)
I only buy movies through iTunes because they let you download an actual (DRM'd) video file, which can then be de-DRM'd. Unfortunately, recent versions of iTunes have broken all DRM removal software. I have a virtual machine with an old copy of iTunes for any new movie purchases, but if that ever stops working I won't be buying any more movies either.
I've just accepted that I'll only be able to watch things once and that's fine, I have much better things to do with my life than watch movies (like starting arguments on HN.)