I'm going on vacation, so I thought I would set my 41 listings to 30 days handling time so as not to lose my watchers.
I used Edit listings in bulk. It did change handling time for the listings, but the estimated delivery dates displayed to potential buyers in the item description OR Shipping & Handling did not update to the estimated correct delivery window.
I guess I'll try the Time Away function, because doing this in Edit listings in bulk definitely DID NOT WORK.