Hi @limpeter, thanks for messaging today!
In general, all plans have at least 30 days to recover data, and the premium plans have 180 days. Incidentally, upgrading to a premium plan wouldn’t allow you to retroactively recover files deleted longer than 30 days ago.
Unfortunately, it wouldn’t be possible to recover files deleted 3 years ago. I’m sorry I can't be more helpful on this matter.
If there anything else I can assist with, please let me know.