Technology Review has a short article by Ed Tenner on the productivity of inventors and scientists as they age, "Megascope: Live Long and Tinker".  The article seems to take seriously the myth that mathematicians and physicists do all their best work before the age of 40.  But most of the experimental scientists and engineers I know, including the majority of biologists I've run into, just get better with age.  It takes quite a while to learn all the tricks of the trade and to accumulate enough knowledge to start putting together pieces that don't obviously fit.  The same, I find, is true of inventing.  The more you know, and the more skills you acquire, the more you are able to produce.

This doesn't mean the process of inventing gets any faster, unfortunately...