For example, triple layer training underwear for kids, or maybe even with clothes, triple layer. At least three fold armor. Note, how in the Iliad, when the ancient heroes were fighting, at least three fold brass helped prevent them from dying.

Also the ultimate luxury; triple ply toilet paper?

Note what makes the Tesla model S Plaid so phenomenal is the triple electric motor.

In terms of kids, maybe the ideal number of kids is three kids?