Sorry for the noob question. TL DR is the title + how long will it take for the data to started getting corrupted?
Some back story: i'm "the media guy" for my workplace and I tend to keep all the RAW photos, videos, all the rest of it, on my own drives. Now that I'm moving to another branch office, I might not need the data to be accessed as frequently, so I'm planning to only put them in a 2 TB ext 2.5' HDD that has been serving as the on site backup for those files in the first place for about 2 years, and may not touch it for a long time. The main copies are in an equally large ext SSD, which I intend to delete after I have completely moved office. I do have an off site backup.
Will rot away on anything, use or no use, at least in this universe. It's called entropy. Have multiple copies, check them periodically and refresh as they die.
To the best of my knowledge and reading many insightful posts here, magnetic HDD have a higher chance preserving data if stored in good conditions (no water or humidity, far from magnetic fields, …). SSDs as I was told need to be powered in order to preserve data begging the question about the usefulness of external SSDs.
Unless the hdd is stored in a high moisture environment, your data should be safe enough. Worst case, the spindle of the motor gets stuck but even there are ways to get the data pulled