Set the expiration time to the current time plus the expriation grace by default

src/main/java/com/sk89q/worldedit/LocalSession.java

@@ -55,7 +55,7 @@ public class LocalSession {
 
     private LocalConfiguration config;
 
-    private long expirationTime = 0;
+    private long expirationTime = System.currentTimeMillis() + EXPIRATION_GRACE;
     private RegionSelector selector = new CuboidRegionSelector();
     private boolean placeAtPos1 = false;
     private LinkedList<EditSession> history = new LinkedList<EditSession>();