I have yet another treaty option you can now set!

CITY TREATY <#> DURATION <in-game weeks>
- (Optional) Draft a duration limit upon the treaty, which once expired
will dissolve the treaty by mutual agreement.

This will allow you to make treaties expire automatically. Do note that it is based upon in-game weeks, which is equal to one real life day (HELP TIME).

Enjoy!

Penned by my hand on Gosday, the 12th of Midsummer, in the year 504 MA.