14-18 months in one case. Solid guy--must have a good sponsor.
Another sim bust from 24 months back or so got his second shot at about 18 months after original shot and made it.
I think MGT knows its a tough interview, and no screening process is perfect. Also--if you aren't a bit nervous (in today's environment anyway...) when interviewing I don't think you are human. Sometimes nerves can trip up even the best of guys and gals.
I don't know it for fact, but I'm sure these 2nd try folks had some good sponsors who burned some serious green stamps to get them another shot.