My game is in the year 2054, which represents about 4 weeks of play at about 2 hours a night. I have 5 extrasolar colonies, with all the micromanagement material shuffling that involves. Last night, in the midst of what was apparently a huge NPR space battle, the game just locks. No error box, just sits there on the same date & time for half an hour. When I try opening and minimizing the windows, I get "Aurora is not responding". Aargh. My most recent save duplicates the problem when I reload. Fortunately, I have a six months earlier save which is apparently free of the problem.
My point being, several saves over a period of time is probably a good idea. When people around here suggest this, they are right.