Events that have already expired when they are inserted have their expiration times changed to the insertion time, which will not expire until the clock ticks at least once.

Isee the following in `drools-core/src/main/java/org/drools/core/phreak/PropagationEntry.java`:

long effectiveEnd = eventFactHandle.getEndTimestamp() + expirationOffset;
long nextTimestamp = Math.max( insertionTime,
                                    effectiveEnd >= 0 ? effectiveEnd : Long.MAX_VALUE );

 if (nextTimestamp < workingMemory.getTimerService().getCurrentTime())

So if current time is still insertion time, the event is not expired.