I couldn't remember the time-frame either. I thought it was 70 days so I removed that app from fb, waited 70 + until the next new season.
If I had known I would have reset it to lvl 1 first - any small cash bonus+6* has a bigger impact at lvl 1 imo.
PS. I also took the opportunity to restart it by invite. That way I got the 'new team' on the account to jump to my other teams sever.