Thanks for all of the replies.
If you don't have time to provide enrichment to all your fish, then you probably need to keep fewer fish.
That's a good point. I was thinking about getting a second tank to put next to one of my existing tanks (I'd cover the side so they wouldn't drive each other crazy), so I don't think that it would add much to the effort. When I go and sit there to talk to Shmuel, I could talk to the other one as well. My second one is in my office so I see him more, he's right there when I'm on the computer.
In terms of water changes, it might actually be easier because I could fill a full bucket to do the tanks rather than having to measure out water conditioner for smaller volumes.
Luckily I don't live in a hurricane (cyclone here) district so evacuation isn't something I have to deal with on a regular basis (never so far, thank goodness).
I think if your ever starting to feel stressed about taking care of them, don't get more. That means you've reached your limit.
Yes, I was trying to figure it out before ending up stressed. I suppose that was rather optimistic. I think a third wouldn't add significantly to my stress levels, unless it or the others got sick.
I can't imagine having 50 fish, that sounds like a lot of work....
Thanks again, everyone. It's been helpful.