We regularly check the EA Service Updates page for information about retirements, with the most recent Maxis title being DarkSpore in March 2016.
EA has recently updated this site to include The Sims 4 Gallery App, which launched shortly after The Sims 4, that allows you to browse items on the gallery and set them to download on your PC game.
The Sims 4 Gallery app will sadly be retired on the 11th August 2017, one month from posting this.
If you’re a user of this, then it will no longer work from this date, nor will it be available on the app store.
You can still download and browse items on The Sims 4 gallery on TheSims.com, and in The Sims 4 game itself.