https://forum-en.gw2archive.eu/forum/info/news/Update-Alliance-Supplies-Found-Items/first#post3750166
“As of March 18th, Alliance Supplies will stop dropping and you will not be able to receive any new Found Belongings or Found Heirlooms. Related to this, you will no longer be able to turn in Found Belongings and Found Heirlooms for items.”
Seems like we just went through this with the Scarlet Lair Cyphers. There are going to be players who will still have these items to turn in after 3/18. It would be really nice if those NPCs stuck around a little while to let the stragglers catch up.