Let's be honest here, "good behavior" is extremely easy to demonstrate in prison where everyone else is constantly getting in fights, beating up guards, etc. It's not a high bar and a person like SBF should easily be able to do that.
There is many other ways to get written up and lose time credits like sharing commissary, having too many books, and sometimes fighting is not optional if your cellmates are into stupid things and drag you with them.
It depends if he is sent to a USP like regular federal convicts or club fed minimum because of his connections. Typically club fed you can only get through a plea bargain like Madoff or through years of good time credits.
