I have given up trying to figure out the poo thing.
When Gabby was a few weeks old, she had poo in just about every single nappy.
Then, after a while, she started doing one every second day (and usually after her first morning nap).
Now she randomly poos at all different times a day... twice sometimes three times a day. Drives me nuts!! But I guess that's what solid food does (also she has recently been having more formula and less BM).

I think it varies but, if you're worried, definitely speak to someone about it.