Ask HN: What Backup Triage system do you use?

How do you triage personal information and documents for various tiers of archiving and retention?

I'm considering a person information system backup and retention system. Classic backup strategies like 3,2,1 (3 backups, 2 different types of media, 1 offsite) make sense, but how much is reasonable to store to really try and keep no matter what? 100MB, 1GB, 1TB?