There's a rhyme to their reason, or is it a reason to their rhyme? lol.

They are fairly predictable if you keep track of sheds, watch their behavior like bowl wrapping, building, and watch for a glow after shed, and then the ovy and then the prelay shed.
They may not do it all in the exact time frame, trust me they don't, but they go through the same motions and same routines.