Mine was three months. Depending on the malady, it could require a board review, which tend to occur on three month intervals. Or it could go before an individual FAA Flight Surgeon. Once you have jumped through all the "hoops" to build a viable file, the clock will seem to tick very slowly from then on. As others have said, warp speed will come once your medical is in Delta's hands. I was reinstated on payroll within three days. In my case, training (IQ) took long enough that I had plenty of time to make up a backlog of 20 dozen QCQ courses and all the systems distance learning, but your experience could be much more rapid. Either way, pay and benefits kick in pronto. Best of luck navigating the final push to getting back in a Delta pilot seat. Welcome back!