The, uh, “Arch” installation on one of my laptops is from 2016 (the oldest one had bad RAM so suffered from file corruption and needed a reinstall last year). Other people will have older installations.
This is one of the key benefits of a well-maintained rolling-release distribution: it just keeps rolling.
Of course, if you regularly install and remove a load of random stuff then configuration files might be left behind, and reconfiguring things or not actively maintaining things then something might break, so wiping then might make sense. However, that sort of testing is better done in a VM so it’s isolated and trivial to wipe.
This would be especially important for OS’s like that one from Redmond, which does tend to accumulate all sorts of cruft. Far less so (if not completely not so) for rolling release distributions.
But given that, sometimes it might be quicker to reinstall than clean up (lol) after some years. Especially if you’re prone to install lots of stuff that you never use.
YouTube, Reddit, and various “tech” websites are terrible sources of information, especially when it comes to Linux. You should never blindly follow a “tutorial” from such places (in general, you shouldn’t do things you do not understand).
Usually, whenever you need to figure out something specific to Arch, the best place to find information is the ArchWiki.
Active forums, like this one, are also pretty good sources of information, since if you spread misinformation here, it typically gets corrected by more knowledgeable people, like @dalto.
I only install EndeavourOS once on a given hardware. When I change hardware, I typically just install the OS, instead of using an existing installation (though the latter is entirely possible, as well).
I keep reinstalling eos every now and then cause i cant make up my mind on which de i should choose, i will set things up kde only to mindlessly load up my usb again to nuke it and reinstall gnome, then i will reinstall kde again and move again to gnome, i seriously need help.
Whether or not to reinstall your system is entirely on you.
The pacman package manager is the best package manager created for a rolling release and when you stick to that you will never have to reinstall your system.
Windows is well-known to accumulate useless files and cluttering with saved versions.
Ubuntu is Debian based and while it is technically possible to avoid it is well-known to recommend reinstall on every release - or using LTS which boils down to once every 2. year.
Years ago it was a pain to reinstall a system - but with modern cpu’s and nvme - time is no longer an issue - and if you keep your data on separate disks it can be super simple to restore a workstation.
I have - over the years - developed a routine making my downtime for reinstallation 10-15 minutes.
I do it sometimes - simply to start from scratch - only copying back select configs.
You still don’t need to Reinstall that is new user mindset. my 1st arch install lasted 12 years in that time it had every DE, WM at one time or another just one base install, but when the h/d died i installed a SSD and gnome3 and have not bothered since as i’m now old and know what i expect from a DE. lol. Read the wiki on maintainance and cleaning its the same base only the DE/wm changes and its more fun doing it your way.