Per AFPC Recall Shop just 2 months ago: "Those who retired from the Regular Air Force do not have to apply for retirement. Prior to their separation date, they will be issued orders reverting them to retirement."

I don't know how early those orders will magically appear. If you remember from the first time you retired, you had to apply at least 6 months prior, even if it was a mandatory retirement. There was a guy in my unit who didn't realize he had to retire at 20 as a passed-over Maj (back then), and at 6 months prior he got a note asking him why he hadn't applied for retirement. Hopefully it'll automatically generate something 6 months prior to your DOS.