It can change right up until departure time.
For example, I'm flying TBS-DOH tonight. My flight to Tbilisi 2 weeks ago had recliners, but this A320 route has switched to lie flats for the past week with only 1 exception.
Right now EF is showing the 28-row Y configuration (meaning lie flats), but I'll only know for sure after DOH-TBS takes off and I can see the aircraft registration on FR24.