I replaced my 211 with an 215 during my last annual, because that 211
(still working) is at least 400 hr old if not much older, and I
couldn't find any reference to its age in my log book.

The 215 works fine. It suppose to have better cooling due to the
cooling fins. I can't speak to its life 'cause it has only been about
75 hours. I do however heard that good overhauled vacuum pumps on 4
cylinder engines can easily last about 1000 hrs, so a 400 hr
replacement interval can generally avoid failures. The life of vacuum
pumps on 6 cylinder engines is significantly shorter due to higher
rotation speed of the auxiliary shaft (?). If the vacuum pumps are
used to power de-icing boots they are even less reliable.