Hi A., firsat of all starting and stoping is never a good idea, all it does is confuse the child. The body works like a machine, I don't believe a child or anyone can hold urine for 18 hours, or poop for 30 hours, the body won't let you do that, it will automaticaly rid itself of waste. At almost 4 if he is a normal other wise healthy child there is no reason whay at almost 4 years old and not be potty trained, I raised 3 kids of my own and i have potty trained I don't know how many kids over the past 11 years in my daycare, and through my experiences i have learned that the failure in potty training is more about the parents than the child, the fact that the accidents don't bother you tells me a lot about your type of training, For example, I have a little girl in my day care who will be 3 in October, at home with her mom she has what her mom calls accidents, and she was wearing a pull up at night, well she is staying with me this who month of August while her mom is deployed, she has not wet her pants once, and she has been dry every morning sense August first, no pull ups at night, if she wets her pants at home and then she cries, her mom hugs her and says that's ok you had a accident, if she'soing to get hugs for weting on herself of course she is going to wet on her self, with me she gets hugs for staying dry, and she has been potty trained sense she turned 2, but when her mom came off of west-pac, she took a few steps backwards, but not with me, it's all in how you do it, waithing until he is almost 4 is crazy A., mine 3 were potty trained by 21, months, 19 months and 22 months. I wish you well. J.