Thanks. I just didn't interpret your comment right initially and thought there was maybe a way to store the XP for later.
I agree that collecting it in advance and losing overnight regeneration is the way to go. I wouldn't want to risk it. At level 197, the dragon ingot waiting in my caravan is going to net me about 2.5M energy, so I can deal with losing my 85k overnight.
As I mentioned, I plan to send out some caravans later tonight and I will report back. I'll do both short and long turnaround to see if there is any difference in yield by ending vs. collection time.
I wish I had looked into the XP thing earlier in the week. As a mobile player not too familiar with pillars I assumed I would only spend the free ticket (I don't like wasting my precious gems!)
Today doing some calculations I have realized it would be well worth it for many of the pillar equivalents. At my level in China, rubies and amethysts (I don't have near enough unfortunately), dragon ingot, but going down the list even to iron, bronze etc can be pretty good value depending on your gem stock. I'll know to plan better for next time.
For all the grumbling about the changes, it definitely adds a much more strategic component to the caravan and double production week than was there before.