It can be 3 weeks to 9 months. No rhyme or reason. You haven’t listed your country ,. Z but it’s worth confirming with your country’s consulate that you
must return your current payout when applying to renew. I know Australia used to have this policy.. But they no longer do., they just cancel the old passport electronically. If you do have to send it with your application, you could request an ADIT stamp as evidence of your LPR status. It is a separate piece of paper that will have your details , photo and the USCIS stamp
https://www.uscis.gov/newsroom/alerts/uscis-announces-additional-mail-delivery-process-for-receiving-adit-stamp