Stop Not Defending and Help Your Neighbors by Visiting KL

Just attempted a visit to KL with 2 shields above the small brown house farm I built for this event (which have been there for 2 days now castles were at 20), and they were gone. How long is the time for castles at level 20? Just raise the recycle to level 22 since notice the price drop, just to see what each level brought. Got 2 more walls & don't plan on raising castle levels any further.