Drive failures are really rare until they happen when your data is personal experience of a few devices. When you worry about a data centre or n and or rather a lot of other systems with storage then you realise that it happens with monotonous regularity.
Now keeping a few short copies is also fine provided you don't make mistakes. Have you ever wanted to recover from a cock up you did six months ago or three years ago?
You do offsite (Tarsnap), so you have covered off local failures - cool.
Everyone's needs are different and the value they place on their data is different but I would respectfully suggest that you think really hard about how important some bits of your data are and protect them appropriately.
My Tarsnap backups are versioned so I can recover dotfiles and projects from virtually any week several years back. And the projects themselves are usually under git.
>I also rsync my entire home directory to an external drive every other week or so.
This is what I do as well, just not quite as often. Sometimes I wonder if I should switch to something like rdiff-backup to get snapshots, but that would only really be useful if I accidentally deleted a file and didn't notice for a while, for instance, which in practice is not a serious problem.
If I had more time and inclination, I might set up a small 2-drive RAIDed NAS box, and do automated regular backups to that. But for my laptop PC, just doing regular syncs to an external HD seems to be fine for now.
My Arch and Gentoo installs have gone somewhat further than that 8)
Admittedly I'm not sure that you can consider one of them that went from i386 to amd64 as the same install simply because /var/lib/portage/world and /etc/portage/ (plus a few other bits) are the same. I still use it and it's on its fifth or sixth incarnation as my current laptop.
My installation of Ubuntu is so standard that I'm one apt install and rsync (of the home directory) away from the same result and don't have to manually configure LVM, encryption, etc.
The important stuff (projects, dotfiles) I keep on Tarsnap. I also rsync my entire home directory to an external drive every other week or so.
Similar for servers but I do back up /etc as well.