You don't need to use the same self-select PIN forever, you can choose a new one (for use next time) each year.
You don't need the 5 digit PIN at all if your prior AGI is known, and IRS has the same number on file for you.
It's best to keep track of your 5-digit PIN since AGI matching problems abound. You can e-file with the 5-digit PIN alone (unless IRS has added you to the 6-digit IP PIN list too).
