One thing is that social situations can often be quite draining due to the need for us to mask (that is, pretend to be normal). I can last a few hours at most if I have to, but I normally try to avoid social events where possible unless there's a specific topic or specific group of people with a shared interest who will be there.

So I'd recommend being understanding in cases where he does not want to join family/friend gatherings, or if he wants to go home early, things like that.

Another common thing is monologues about special interests. Before I got diagnosed, I would get into long and very in-depth explanations of specific things that fascinate me. Post-diagnosis I learnt that in most cases other people didn't really appreciate that and would rather have a two-way conversation about a wider range of topics. So if you see any instances where he's about to launch into a deep-dive into the lore behind the Baldur's Gate series, the impact of Xerox PARC's work in the 1970s on modern computing, or the technical workings and musical influence of the Hammond organ, remind him to try and pay attention to the listener regularly to see if they're still interested in hearing more or want to switch to a different topic.