WMDE Technical Wishes/Watchlist Expiry
The wish of expiring watched items
The Watchlist expiry project offers a way for users to add a page to their watchlist that will automatically expire after a day, a week, a month or a custom time limit. It was a wish on the German-speaking Community Wishlist Survey 2013 and #12 on the International Community Wishlist Survey 2016.
The WMDE team started working on watchlist expiry in the beginning of 2016. It quickly turned out that it would make sense to refactor the watched item code, before starting to implement the feature. So this is what they did for four months. More details about the refactoring can be found here. Since one change of the refactoring had to be applied to all existing wikis via a database update. As of May 2017, this change is implemened in all databases of all wikis.
You can see more details about the realization of the wish in this ticket.