Yeah, that's another problem w/ expensive lenses, some guys just don't use them much 'cause they are afraid they'd damage or spoil the lens if they use it too often. That's kinda waste if you ask me. IMO the more you pay for a lens, the more you should use it to get the money worth
Mine in my dry cabinet most of the time and hardly use them. Just keeping it for the time being and waiting to see if Pentax come up with any digital FF.