At what age do most kids complete full potty training where they make it through most nights staying dry?

You really can't train or teach a child to be dry at night. They have to develop the physical capability to wake up when they need to pee, and get to the bathroom, or else for their bladder to hold onto it. It's a physical maturity thing which can come at a wide variety of ages. Some seem to 'get' this before they get daytime potty use; I've known babies dry at night by 18 months. Others manage to use the toilet in the daytime reliably at around two-and-a-half, but might not be dry at night until four or five, sometimes even older.

You can try reducing fluids in the evening, and making sure the child goes to the toilet before bed, but otherwise just wait till it happens naturally.

Depends on development and how much effort the parents put into potty training there child. Some take longer then others. My daughter is 2 1/2 and half way potty trained.

night time training is more difficult and some people argue that it takes a child until 3-4 years old to completely master this

Well my daughter been potty trained for about ten month....and she is two...it depend on the child and how often you take him or her. It also depend on how much you give him or her to drink. I stop giving my kid water juice milk at 730 pm

Every child is different. My 2yo has been toilet trained since around his first birthday and dry nights basically the sane time he got the hang of using the toilet properly.