Frequent electric shocks seem to be the way to do it then.

You might want to rethink your assumptions here. Stress generally makes you less productive. And there are plenty of long-lived people of high accomplishment.

What do you mean by "stimulating your brain"?

If you mean being mentally active all the time, in the long run that'll make you less productive, not more.

Why not both? Meditation, mindfulness, equanimity... + curiosity, mental training, math, programming, challenging yourself!

well if by that stimulation you mean also stress, than certainly you are shortening your lifespan, possibly significantly.

"The light that burns twice as bright burns half as long"

Well life span is not the point of the story imho, so don't worry about it. The data will prove that too in time.