I think 4:00 a player should be the limit. I like the 1min interval as well, you should be able to take as long as you want really. But with 4:00 you only get 30 seconds on average per rock, which is fair. The first few rocks usually take 2 seconds to get the shot off, no thinking time. It's only because, time is never a factor in this game, this may put a little more pressure on the overall time. Also some players will accept a challenge and not play hoping you quit to try to get ratings points. So this would make their time limit go just that much faster. Anyway just an idea.