mine stay protected in the closet. =]
My bag is pretty well protected with the standard lowepro padding, so why add an extra step when switching lenses? On a hot day, the last thing you want to do is spend more time sweating in between lens changes rather than getting the shot and finding some shade to take a break at.
if i had owned the 85L II, i probably would use the lens case as the size of that lens is huge!