OpenSUSE considers dropping reiserfs

For old disks kept as archives (not necessarily powered-on all the time in a cloud).

For files that you don't need anymore but you prefer to keep as backup (for 10 years or 20 years), a practice is to have two disks with the same content, but disconnected. From time to time, you may check that the content is still readable.

That way it uses less energy.

Me, roughly one month ago when I discovered the hard way that ext4 is not made for many files. Yes, you can use tune2fs at runtime to raise the file limit per directory (large_dir option), but there is no way to undo that except throwing the filesystem away and recreating it from scratch.
GRUB won't boot from an ext4 filesystem with large_dir active, so I suddenly had a non-bootable system with no spare capacity to recreate a working state. Lesson learned.

Then I remembered that ReiserFS (which I had used many years ago when it was more stable than ext3) has no inodes and thus no inode limit. And there are tools to do an in-place conversion to ReiserFS. However, the looming deprecation of ReiserFS and its non-maintenance seem to have accumulated bugs slightly faster than ext4 where bugs are introduced through maintenance (b5776e7). So... ReiserFS was not a choice anymore.

In the end I chose XFS and recreated everything from scratch.