Interesting you should mention the wardrobe. I had a college math professor once who wore the same pair of khaki pants the entire semester (LOL). Rational for the Brady's lack of dress variety could be any of the following:
1. Probably the show was on a budget and couldn't afford an extravagant wardrobe.
2. They could have possibly produced more than one episode in a given day.
3. Brady kids refused to change their clothes or dress up and threw a tantrum forcing Carol to give in.
Anyway, I hope they laundered their clothes regularly :-).