Minimum for president is 35, senate is 30, house is 25. For one, I think those ages are “sufficiently youthful” to be generally representative of current modern concerns, all other things aside. They could easily be some years younger, possibly eliminated entirely, on the same basis as there is not a current upper age limit: let people be elected on their individual merits, and not exclude people on the basis of age.

I agree that there being a minimum age limit without an upper limit is contradictory, but a better solution would be to lower or eliminate the minimum. Perhaps some other kind of metric could be employed in place of a minimum age limit for federal office, like “having served as an elected official at the State level for two years.”