old post, but I so wonder why you got downwoted for saying it like it is. a good isp will give you a /56, the minimum best practice. a great isp will give you a /48 you’r router will also participate in the wan /64, but that is just the uplink, and not something that will be used on the lan. https://www.ripe.net/publications/docs/ripe-690/#4--size-of-end-user-prefix-assignment---48---56-or-something-else-

How often depends on how much work it is to recreate, or the consequences of loosing data.

Some systems do not have real data locally, get a backup every week. Most get a nightly backup. Some with a high rate of change , get a lunch/middle of the workday run.
Some have hourly backups/snapshots, where recreating data is impossible. CriticL databases have hourly + transaction log streaming offsite.

How long to keep a history depends on how likely an error can go unnoticed but minimum 14 days. Most have 10 dailes + 5 weeky + 6 monthly + 1 yearly.

If you have paper recipes and can recreate data lost easily. Daily seems fine.

Never canceling that. I’d rather rewatch anything d20 over anything on netflix.