My daughter has been potty trained (daytime only) for about 9 months now, and has yet to poop on the potty. She deliberately waits for naps and nighttime (she's quite regular) when she knows she'll have a diaper on. I haven't been making a big deal about it, mainly because she's only had one poop accident since we started potty training, and I have no idea what to do other than encourage her to use the potty. Should I be doing something about this? Will it just happen over by itself over time? When does it become a problem? She's 27 months, in case that's relevant.