I think the idea is a good one. Personally, I'd make the shortest times be reserved specifically for
players who have been in the game less than a month and
players who have been in the game less than six months. Then make the "standard" length for a noble with
no feudal or government position be 5 days.
Then, on the high end, as others have said, I'd pull it in a bit—maybe make Dukes 12 days, government members 16, and rulers 25, or something along those lines. I think 30 for government members and 40 for rulers is too steep.
There's something else to consider here, too: Should we make prison no longer count as inactivity for the purposes of losing positions? Because right now, if we did this, it would just cause all the position-holders to time out after 5 days, so someone new could be elected/appointed. Then the poor old ruler just gets to languish in prison for the next 5 weeks without any position or anything.
As a final note, I
like the idea of the realm being able to pay a ransom for a captured government member. That would make a very interesting dynamic...particularly if the government member in question isn't universally loved
