It won't rise much beyond that, since you only get one update per package. Whether it's upgrading Firefox from version 120 to 121 or to version 130, it doesn't change much in terms of download size, nor the number of updates.
At least, I assume, Arch doesn't do differential updates. On some of the slower-moving distributions, they only make you download the actual changes to the files within the packages. In that case, jumping to 121 vs. 130 would make more of a difference.
If you do want lots of package updates, you need lots of packages. The texlive-full package is always a fun one in that regard...
I have updated arch systems that had not been powered on for years before. It was fine. No issues what so ever. Arch is not some flaky distro that breaks if you look away for a minute. My main system has had had the same install for over 5 years now and I regularly forget to update it for months at a time. Again, no issues.
Well in an immutable distro, there is little to no chance for the system to end up in an unusable state (I guess it is the same for distros which apply the updates atomically). Traditional distros are far more likely to bork when so much shit is updated at once
So you neglected the operating systems maintained regularly, despite it being a rolling release? I assume you didn't read the manual intervention instructions that are posted regularly too. I don't understand people using a rolling release and then not caring about the maintenance. Off course it won't end very well.
I used Tumbleweed for eight years with no problems. I only moved to EndeavourOS because Suse bared their corporate teeth and I got fed up being a couple of generations behind on the Nvidia drivers. EndeavourOS is also good.
welp, looks like you don't use python virtualenvs... well i guess jokes on you all your shit is probably broken now (and as a bonus, that's probably a big part of the donwload size as well) :p
Recently updated a nixos machine that was on the shelf for five years or so. A few options and packages had been renamed, fixed those, upgrade completed with zero problems.
Only issue with this update was a maintainer's keyring had expired and been replaced, so his packages didn't pass the signing check. After re-installing the keyring, the whole think works fine.