I don't really mind. Even when they were potty-training, I wasn't one to ask them every-so-often. I usually asked right before we needed to leave the house or a place. I just hate it when...um...I need to go so I ask them first. Most times they say "No!" Then when I finally get in there one of them will be banging on the door suddenly needing to go.
And occasionally this would happen shortly after leaving the house so the rule now is that if they don't think they need to go...they still must sit on the toilet and count to 30 haha.