Perhaps you changed your oil before this tour. Different oils have different additives such as seal swellers and conditioners already. Maybe you changed to something with less additives and that caused the leak.
I've thought about that. The dealer actually changed the oil when I had them check the valve clearances a few weeks before the tour, even though I didn't request they do so. Even though I wasn't charged for it (on the invoice anyway), I doubt they used the Motorex Top Speed 4T that I use.
I just changed it yesterday using the Motorex, so will see if that helps.