Once your Form I-131 is approved, USCIS issues an Advance Parole, which can be valid for a period of 1 or 2 years. If you will be outside of the USA for a longer period, you may eventually need to apply for renewal of your travel document.
To renew your Advance Parole Document (I-512L or I-512), you should file Form I-131, Application for Travel Document, up to 120 days before the date when your current Advance Parole expires.
We recommend early filings whenever possible, especially when you have a single card for both an Advance Parole and an Employment Authorization Document. Plan carefully the application filing date and take into account any possible trips outside the USA.