You misunderstand. if you are operating only under the assumption that your voting power should be proportional to the time you have left to live, then there's a pretty clear age-power relationship.

If you add an assumption about life experience though, You're going to have to be a lot more specific to explain how these two functions interact. why is the optimum in the middle? Why isn't it bumpy?

As soon as you start adding other factors into your weighting function, I don't know how you can be confident in the shape of your graph without being precise with your functions.

To be fair though, I think that there's a pretty good argument for inverse age weighting. If you're 20, you will eventually have to be 35, so it wouldn't make any sense for you to screw over 35 year olds. If you're 35 though, you'll never be 20 again. There is no incentive for you to not screw over 20 year olds. (unless you have kids, but at that point, everyone has equal investment in society and the premise falls apart).

And on the other hand, old people's poor decisions are often blamed on their age as well. The elderly are prime targets for most scams because they are perceived as more likely to fall for them.