[JJ_SO]

Clearly a job for our man in Lebanon! Go and get yourself a testchart, a couple of analyze programs and test the data of used lenses, see if the light burns out the glass, if the AF gets stutters and count the dust particles inside of each indivdual lens. Maybe you can find out this way how much one single lens was stressed and we can tell you afterwards how relevant that knowledge is for our lenses - being much more or much less stressed than your copy... If you want to get results, don't waste (other people's) time, just do it yourself!