Most of the time, I keep my lens detached from the body as when comes to events like press conferences, I can decide what sort of lens to fit in which body like 70-200mm lens goes to my 30D body and the 16-35mm lens my FF body (1Ds MARK III).
On the go during travelling i attach a lens. too troublesome for me to fish out the camera mount cap and change every now and then and introduce more dust switching, and besides, i might miss shooting something impromptu.
If you are referring to keeping in dry cabinet, i keep them seperated. Mainly because space is becoming a premium :bsmilie:
any significant differences if keeping the lens attached or detach when storing inside the dry cabinet unless space constraint? i normally keep them attached... its easier for me cos i normally shoot using 17-50.. so i juz keep them on...
My 35mm f/2 is my expensive body cap that I leave on almost all the time. Besides with that on, I can switch on and shoot almost instantly. No need to remove lens rear cap and body cap then mount the lens to be ready to shoot.
The only time my body goes without a lens is storage into some bags, especially when I don't expect to shoot within short notice, or when I am storing in the dry cabinet.