We realize that good shoes are a decent investment nowadays, but knowing when to swap out your old footwear for a fresh pair can save you from a lot of discomfort, injury, and unnecessary strain.

Antonia Saint Dunbar, cofounder of the period underwear brand Thinx, loves the way she feels when she’s wearing heels. “It has a divine geometry,” she says. “It creates a perfect pitch for your body, ...