I started a batch of Leuchtenbergia principis seeds on 8 May. I wasn't sure what percentage would germinate, so I started a lot (56, which isn't even half the number I got1). I noticed the first seedlings on 15 May, and new ones keep popping up. So I will soon have way, way too many baby Leuchtenbergias, with enough seeds to make way, way more.
So far, they don't look like much,
and Leuchtenbergias are slow-growing plants besides, so they'll probably continue to not look like much for quite a while, but that's just a guess. In any case, things seem to be working as intended so far, so that's something.
Readers who have always wanted to grow a Leuchtenbergia principis but have never been able to find one for sale (which I assume is probably most of you), let me know: I can probably hook you up with some seeds. I don't know how delicate the seedlings are yet, but mature plants are very easy to grow as long as you can supply them with adequate light.2 Hopefully the seedlings won't be significantly harder to deal with.
2 Leuchtenbergia rates a 2.0 on the most current incarnation of the PATSP scale, virtually all of which is due to their need for stronger light than most people can easily provide indoors.