Typically, time on equals time off.... and you start counting after finishing PCT.
PCT, even a simple course of Nolva, will protect your natural ability to produce your own test, which helps you keep your gains. No PCT debalances your body and puts you into a catabolic state which EATS your hard earned gains.
As for a follow up cycle... What you take depends on your goals. IMHO, you could add some more mass before worrying about winny (you already look like your BF is under control). Test alone will keep you lean as long as you eat decently. I'd suggest taking your t400 to 3 injections a week of 1cc each, for 8-10 weeks. Keep Aromasin on hand to control estrogen. Have a bottle of Nolvadex on hand to run PCT.
As for when you do this... when did your last cycle end? If it's been more than 4 weeks, PCT may be a waste of effort at this point. Wait till you elapse the same amount of time you were "on" last time before starting a second cycle.