Hey cheers, I bet I'm around a decade on the same install of Arch too. That spans 3 machines. The trick for me is hot swap backups. I do an rsync backup of the drive to an identical disk (nowadays a 1TB 980 Evo) and then immediately swap the backup drive to the main drive. I have little helper scripts to format drives, do backups and automatically update fstab and the boot config. So new machine no problem, rsync the files into it and boot it up and I have everything exactly as it should be.

Now and again I'll do some package spelunking (pacman makes this straightforward) and clean out cobwebs. Next on my list is my emacs config which is like 15 years old and a couple generations out of date. I wouldn't care but startup times are slowing down and there is a lot of great ideas and packages to solve this problem. Just need the time, it's a few hours here and there, but easily enough to keep Arch going forever!