The time consuming part is setting a scene up. Characters and their clothes, environment/background assets, lighting and so on. Once that's done, you start creating your renders.
Take for example the current update's Mayor scene. After the initial setup, you start positioning the characters, their facial expressions etc. as the scene moves on to fit the narrative. One render with Jess standing next to the Mayor, the next one with her sitting on his desk, and so on. A developer with a brain would usually save their scenes and render stuff overnight so they don't have to render while working, forcing a break inbetween every render unless they have more than one rig at their disposal.
Setting a scene up, as mentioned, is only done once. You're not redoing everything from scratch for every render. Things like clothing, facial expressions and lighting may potentially need slight adjustments to fit the different poses your characters strike and the story you want to tell, but once the hard part (initial setup) is done, creating renders with what you have is usually a pretty quick task unless your name is stoperArt and it takes you an entire day to change the pose of a single character.
Now, that is obviously simplified and technicalities are left out pretty much entirely, but you get the picture hopefully.
So yes, stoper should be able to release an update every 2-3 months if they're the size of his current releases. He used to do exactly that, but then everything turned into a massive shitshow.