I always shut my doors unless it's really muggy and I want as much airflow as possible, or there's something to watch like a sunset or sunrise.
I quite like the enclosed feel I get with the doors shut. If there's a prevailing wind coming through camp I'll close the end off into the wind and use the opposite end for access.
When the rain starts coming down sideways I like the extra protection too, winds are kind of swirly on our wee island
I've got doors on my Superfly and HG 4S Cuben