I've got a sister-in-law that let her brat do whatever he wanted. Wasn't potty-trained until age 5, in the July just before entering kindergarten, and up to that point, wouldn't even lay down to have his diaper changed. She once made the comment "he just doesn't seem to mind me". I told her "you get what you settle for". Talk about a fly-by.
My sister-in-law has 3 kids, the oldest just graduated from high school (how, I do not know).
This kid growing up, never had a bedtime, he was allowed to stay up as long as he wanted ---- he stays up all night now, and sleeps during the day.
My s-i-l just shrugs her shoulders and says she can't get him to obey her, so she gives up.
Needless to say, this kid is a major brat at 18 ---- he tells his mom to f'off at frequent intervals.