Re: when you say goodbye to diapers
My DD was daytime potty trained at 21 months. When we decided it was time to potty train, during the day we only let her wear cotton panties. No more diapers during the day. The only exception was if we went to a store, I would put on a pull up. Even then I'd wait to go to a store after she just went. But around the house and at the park, only her cotton panties.
At night time I still put on a diaper at first, then pull-up, then when the pull-up was dry in the morning for several days just the regular cotton panties. That was probably around 2 1/2 years that she was night time potty trained. A big part of that I think is their bladder has to be big enough so the bigger they are the more likely they are able to get through the night. We always made sure she went before bedtime too.