There's something to be said for putting off the voting age a few years, to give a chance for people to build-up a bit of pent-up frustration about being messed around with by government, so that when they get tghe vote they see that as more significant.

Forty might be about right. And that stuff about how people inevitably move to the right as they get older is questionable. In the British political scene older Labour people tend to be well to the left of where the party has got to these days. Hence Old Labour, New Labour.

I rather suspect the same would apply with Democrats in the States, especially if you set on one side the essentially non-political cultural matters that are given prominence over hard-core political issues.