Comment by easterncalculus

Couple of things - if you want prefixes to stay the same you can use ULAs for your home network. Not ideal but it's available. The 'right' way to manage this is to use DNS, and just have the prefixes auto-update there, or mDNS. For prefix sizes you should be getting a /56 most of the time, especially from major US ISPs. If you're getting a single /64 it's almost definitely an issue with your router's PD setup.