Or ensuring the spool is still useful 15 years later while everything has migrated to SFP/QSFP

Nah, the remaining spool will be useful for the rest of its/your lifetime, it always comes in handy as a generic 4-pair twisted pair signal cable for any non-ethernet purpose. I’ve used my old spool twice this year; first for an m-bus cable to my power meter and then for a limit switch for my garage door.