Where does it stop? Of course having a bit more room does not hurt, but my view is that if 256GB was not enough for you, 512GB wouldn't be either.
To me it's mostly about learning to mange RAM and storage space on your machine. A lot of stuff does not need to be hoarded on the machine. Move infrequently accessed data to an external drive. Be ruthless about purging stuff you no longer really need. Refuse to run apps that consume tens of GBs of RAM on a whim (looking at you Firefox, I've been impressed with how efficient and stable the Helium browser has been for me). If you are a developer, engineer for efficient use of RAM and storage.
Like I said, 16gb RAM and 512GB storage minimum is nice, but if the fundamental issues that contribute to massive and wasteful use of resources on our machines are not addressed, nothing will be enough.
I think 512GB is a fair minimum for a computer these days, but I agree with your "Where does it stop?" sentiment when it comes to RAM.
If browsing the web takes 12GB of RAM, at what point do we stop chasing after more RAM and instead start demanding better performance and resource usage out of the web?
From observing family members, 256GB is usually fine, but small enough that normal computer use can accidentally fill it up. 512GB provides plenty of headroom for them. 512GB is tight for more involved usage that’s not serious media creation, and 1TB is comfortable. 1TB seems like the realistic minimum for heavier media creation.
>Where does it stop?
I don't know but macOS is making it ever more difficult to manage storage, with lots of random things under "macOS" pushing ~40GB or "System Data" that gets a crapload of unrelated things like podcast [1] downloads, with no easy way to purge.
[1] I spent too much time hunting down ~250GB of missing disk space, and it turns out it was the Podcasts app's cache, while the app itself reported no downloads. I fully expected this to be managed automatically, but was getting out of disk space warnings. It's a mess.