I did it once a few years ago and it was good for a year, I believe. I'm OK with 90 days since Boss has option to fly bid IST w/great seniority [in season] I'd go back repeatedly, as long as I don't have to encounter the same Turkish policewoman who "frisked" me prior to departure...(search that one on nonrev.net for more info--female Rifki? Glad I didn't have to look for a hook on the door)