I'm afraid that pretty much sums it up.
I hate to sound selfish, but frankly, I started the ALC threads for a selfish reason, to improve my own game. I started at Prince and I'm now playing at Immortal level and am close to moving up to Deity. Yay me! Now, I'm not claiming to be a Civ god (despite the name of the next level I'll be challenging), and it's not that I don't still see improvement thanks to these threads, but I'm simply running into the law of diminishing returns. A great deal of effort is required on my part for a much lower return than I used to see.
Ironically, I think I have played enough ALC games so that by now I would have gone through all the original leaders in Civ IV. So in a way, the challenge has been met... sorta, kinda.
But the addition of more leaders in Warlords and BtS made the task Herculean.
So what remains to motivate me? The interaction with the community? Well, I can do that in the other threads on the board, and a lot less effort is required on my part. And I'm focusing more on my writing in my free time these days (and I'm trying to finish off my Princes story thread, for those of you who are following that).
So consider the ALCs retired for the time being. Who knows, one day I may fire them up again, but don't hold your breath.