[yboris]

This probably depends on area of concern. Mathematicians seem to be best in their youth (though of course they can continue amazing work into their late age). Philosophers are often able to write their best work in later stages of their lives.

I know a day (or few) after use of marijuana, when I speak, I'll have to pause for a bit to remember a word I had intended to say. I suspect this can affect problem solving skills too, but so far none of my coding seems to have been affected. Weed seems to me an acceptable trade-off (enjoyment / temporary mental degradation).