Received 24 month extension letter on Oct 30th (LIN filer), of course that was the day AFTER I traveled internationally 😅
However, returned to the US a week later and went through immigration using 18 month letter without any issues!
Update:
Package sent Feb 25th (FedEx)
Package received Mar 1st
Credit card charged Mar 26th
Text notification Mar 30th
NOA received Apr 1st (dated Mar 26th) - LIN facility code