

Hard drives are so variable and failures so unpredictable, I bet you can’t find that information. Most of the actual data about hard drive failures, like Backblaze’s reports, are for drives that don’t spin down.
That said, spin-down has always been used for saving power, not drive lifetime. I would generally assume spinning down never extends lifetime. Even in the case of an external hard drive you plug in once a month - it is very likely going to fail earlier than the drive spinning 24x7.
Also, I wouldn’t shy from keeping the database on the same, fast storage as the OS, even if that’s flash. Move to an external SSD when you can. HDDs have such long seek times.
Indeed, it’s the top issue for number of comments: https://github.com/immich-app/immich/issues/12614
That and this one are really what keeps me stuck in “evaluating”: https://github.com/immich-app/immich/issues/165
Right now, immich just points at a read-only copy of my pictures for trying things out. Nextcloud copies the pictures off device and then deletes them locally -necessary for family who always take long sports videos.