Initially I had thought the same, eg, I've got two 135mm Rodagons, serial numbers not too far apart, one cleaner than the other. I'd thought to strip down the not-so-clean one and hope for the best. If I butchered it, I'd still have my 'good' one in use anyway... But then I thought of how comforting it is having a backup, and how much they'd cost me to replace...
You worry too much...
.::Gary Rowan Higgins
A comfort zone is a wonderful place. But nothing ever grows there.