[img]time based: each character has there own speed, so after a certain about of time you get your go.[/img]
why dont you alter it slightly? on one game i played online, you upgraded your ships engines to give you more speed, and this speed was proportional to how many turns you were given every hour, so my corvette with speed 22 would get me an extra 44 turns to use wisely until the next hour.
to stop ppl just accumulating turns, there would be a limit, i think it was something like 150*speed, once your turns reached that number, it couldnt get any higher