I love to play as much real time as I can, a real sub captain feel. It takes real patiences to do this, as you will travel for hours, if not days, with nothing happening. Then you hear the crew yell and the alarms go off, and its a real heart thupping and adrenilene high. You will feel like you are really there.
One reason I love to play at Raiders of the Deep, as they are not timed missions, and they would rather you play real time to get that real sub commander feeling. If needed you can take two months to finish one mission. Their new Campaign Wolf Hunters is the same way.
Sorry for just ranting, but as I said, its the only way to play, if you have the time.