Yes, I too would like to know why Allender is retiring. But I guess we'll not be able to find out as DHR is very closed mouthed about these things (and a lot of other stuff as well!). Perhaps someone "in the know" will be able to tell us.
I was very concerned when Sherman left some time ago as I thought him very highly regarded, but there appears to have been no adverse impact on DHR's stock price.
By the way, the recent detailed DHR article in Business Week did little to advance DHR's stock price. Cannot figure out why.