You should probably return your child to diapers whenever:
You’ll be in the car for more than an hour or so and would prefer to stop as little as possible; You’re attending a special occasion (a wedding, a funeral, a concert), where you would really resent having to leave to attend to an accident; Your two-year-old or three-year-old goes to bed for the night—or for a nap if she still urinates during naptime; or Your child has quite a number of accidents in quick succession.
This last item gets a little tricky. Toilet training does not always work the first time. If your child doesn’t seem to be getting it, if misses far outnumber hits, if accidents happen, but they happen all over the place, then you may need to put a halt to the experiment for a while. There’s no law that says you need to toilet train your child by a certain date or to succeed the first time. So put it off for a few weeks—or even a few months. But at the same time, try not to use the “dreaded diapers” as a threat. Remember that accidents should not be used to shame or blame your child. It only makes your child feel small to hear you saying something like, “If you don’t stop wetting yourself, you’ll have to go back to wearing baby diapers.” Try to keep in mind that it’s really not your child’s fault if she has frequent accidents. That’s an indicator that your toddler doesn’t yet have control, not that she’s not trying. Maybe you tried toilet training too soon, before your child was really ready. If you do decide to curtail your child’s potty training for a while, try to ignore “helpful” relatives and friends who insist your child should be on the potty by now. Your child will eventually master this skill. If she’s not ready, does it really have to be right now?