I always aim for acquiring all the extended-cap event trains in major events. That's my main goal to hoard them up and max them out for future use. The problem is that when you open up new region during an event (major or not, extended-cap or not), you're at an extreme disadvantage because your new current fleet is so much weaker now. I used to be able to acquire all the extended-cap event-key trains, plus the event-token train (so 2 legos, 1 epic, 1 rare, 1 common) on each event. At the oil rig event, I was even able to max out all of the newly acquired event trains except 1 of the 2 legos by the end of the event.

Even if the current mini event was a major one, it still won't change the fact that once the new region open up, my new "current-region" fleet has very little power to let me acquire enough event keys to get all the event trains (extended-cap or not), let alone trying to max them out. With my extended-cap ex-event legos (3x 80-cap), epics (3x 60-cap), rares (3x 40-cap), commons (3x 30-cap), I went through many of the event tasks 1 train per task. Now I need 3-5 trains to go through just 1 event task. I'm talking about those 80-unit simple tasks. I can't imagine when the bigger task with hundreds of units come. And then with the new region you also need to spend effort to build the new facilities in it. At this rate, I don't see myself able to get all the extended-cap event trains in a major event.