How does a scientist's h-index change over time?

How does a scientist's h-index change over time?

Since its introduction a decade ago the h-index has rapidly become the most frequently used measure of research productivity and citation impact amongst scientists.  It’s far from perfect and has been criticised from a number of perspectives, particularly when used as a blunt tool for assessing a scientist’s “quality”.  Nonetheless it’s a useful measure that allows some comparison within research fields and (I think more importantly) gives individuals one method, amongst any number, of assessing the influence their work is having on their discipline.