I believe the official guideline is 42 days, but there are indications that it is better to use it sooner. However, if it is frozen, it can be used years later. The rest of your comment about emergences is accurate of course. If you can't get your autologous donation when you need it, then you are exposed to the general blood bank supply unless a safe donor is immediately available.
I tried to give blood for my husband in the mid-90s, but they refused to take it. They said that they couldn’t because I was a relative, and they could only take blood from the Red Cross.