I used to be in the habit of popping my cartridge bottom bracket out every 6 months or so and refitting to avoid the risk of it siezing into the shell. Someone on the old ST forum said that they never bothered to do this and that I could damage the shell threads by removing and refitting the cartridge.
I was wondering what the general consensus was on this, should I just leave it be? I always use plenty of copper grease when fitting the BB.
This is STW. No one on here keeps a bike for more than 6 months.
fit/forget/ride
the only time I've had trouble getting BB's out is when I forget the drive side is a reverse thread.
Unless you find lots of water in your frame you shoudl just leave it in and ride (particularly sq taper which last forever).
^what they said^
You'll not do it any harm taking it out every so often unless you are ham fisted and cross the threads each time.
If you've used plenty of copper slip, it will be fine until you need to take it out. However, unless you're a chimp, you'll not do it any harm.
I took the original shimano bb out of my old 1991 carrera earlier this year. It was a bit difficult 
My fat dad held the frame down, I attached a 5 foot scaffold pole to my BB tool... It shifted. But on the basis of that it does seem like it's a good idea to remove or at least slightly loosen and retighten the things at least, oh, once a decade.