Every night is formal night for us. My son just turned 6 and the first request for his birthday gift was a new 3 piece suit (because he had outgrown the one he got for his 5th birthday). He's only 6 and it won't last forever, so I'm enjoying it while I can. It's amazing to me that a such a young age he has a concept of dress codes. Even if we are at home and just going out for dinner, he'll enquire about the dress code before he goes to get dressed.