Conventions are powerful reinforcers of cult mentality.
When you go to a couple of Meetings™ a week, with the same people over and over again, the social aspect becomes a bit stale, and some people have a tendency to miss here and there, because it is the same-ol'-same-ol' pretty much every week.
Conventions, on the other hand, are like a blood transfusion to someone who is severely anemic. It's a different place from the routine. It's with thousands of different people. You go out for dinners to restaurants with The Friends™, you all get excited about the talks, and there's a ritual when socializing at conventions to share what you felt was a highlight from the talks with everyone else, and everyone else shares their highlights with everyone else.
People who attend conventions, though they might be physically tired from the experience, always feel they are Spiritually™ energized. They are on a "high" that can last for quite a while afterward.
You can be sure that there will be talks focused on avoiding Apostates™ or Apostate Reasoning™. So you may want to cool your jets on that front for a bit.
What I'd focus on has nothing to do with the doctrines or beliefs. I'd ask How many times did they talk about donating? How many times did they bring up giving them money? Because that is the central purpose for holding a convention as far as the WTS is concerned. And the Spiritual™ "high" that many JWs are on when they attend a convention keeps them from noticing the many times that cash-flow is a priority.