I shot down a UFO, but a few of my "must have" soldiers are recovering from wounds. I would like to send them in 4 days, or 2 if I had to. Will the crash site disappear or otherwise go bad if I wait too long? If so, how long is too long?
Based on some testing:
On Normal, I have observed several of scout-classed UFOs take between 24 and 48 hours before being "repaired" and disappearing.
On classic, I have observed two scout-classed UFOs taking between 24 an 30+ hours to disappear.
Small sample sizes, and I don't know if bigger ships are more or less likely to take off quickly.