You'll have a bigger update the next time ─ although, that said, I wouldn't advise waiting five years before updating. If you wait too long, then you might run into breakage. Major updates for the Manjaro Stable branch only come once or twice per month anyway.
It depends on how much you've got installed. The more software you have on your system, the bigger the update will be. But it does vary considerably.
That said, the dowloads themselves aren't necessarily that large, due to the fact that the packages are all compressed with
zstd ─ earlier it was with
zstd offers better compression and faster decompression for the same compression ratio.
Manjaro isn't Arch, or at least not when it comes to the Stable branch. Manjaro Unstable corresponds to Arch Stable, but Manjaro takes a little longer to test and bundle the packages.
All in all, I would say that Manjaro Stable is just about the most solid rolling-release distribution out there. I've been using it as my daily driver for almost a year now and I haven't had any major problems with it so far. There are point-release distributions that have more problems than what you'll encounter in Manjaro.