Hello there 0uttajail. There is no update schedule for patches in The Sims 4. The Sims team do not usually announce major patches very far in advance. It's recommended that you check the offical Sims social media channels as they normally announce major patches or hot fix patches closer to the time they are finalised.
0uttajail wrote:It seem like every 3-4 weeks there's an update that doesn't really fix anything
The patches do usually fix a whole wide range of issues, but unfortunately just like any other game that has patches there is always the chance of some new issues slipping into the game. Since The Sims 4 is a live-service game, frequent patches are excpected.