Around 30 years of age,

I would say.

And then the power is reclaimed by the Ministry, and given to the next one...

Yes. And in the time in between, you will work for us in return.

What will it be?

Huh?

You can hand over that power right here if you wish. If you do, it'll also stop gnawing away at your body from here on out.

But...

You would be able to pass it forward no longer.