All HDD will eventually give up the ghost (Confusius 400 BC).
To prevent much teeth gnashing and hair pulling, I believe it is a wise move to have backed up all files which might be needed and which can't be easily replaced or replicated by a new clean installation and installing available apps again.
But; which folders/files should be back up - forgetting the rubbish and data files created since the beginning? (What to do with them is probably more an issue of emotion rather than necessity).
I would appreciate any advice on this subject. Storage space is not a problem, nor is time to backup.