Backups should be regular and accurate enough to trust on restore.

Are you seriously proposing to login every day to 10 different accounts on 5 different web sites, go through a list of 300 contacts, compare them with your word document or piece of paper, and update the ones that you've changed recently?

Or are you suggesting every time you add a contact, remember to write that change down somewhere else too? Possible, but a tad inconvenient and prone to forgetting from time to time.