The stern mouth opens

I was very surprised to find that the clamped face of my Gibbaeum heathii has opened up to reveal a new set of leaves! It has also split along the side (possibly my fault from a light watering?), and there is definitely something new growing in there too - possibly another head? I don't know much about these plants at all - should they be treated like lithops and not watered until the old leaves have shriveled, or does it like to stack leaves like some other types of mesembs?

Exciting times!

For reference, this is what the plant used to look like: