It takes a long time to wear out a Birkenstock, a favorite sandal of Boomers (with or without socks). Here's a comparison of a new pair to an old pair worn daily
Arizona Essentials EVA Black | BIRKENSTOCK
Arizona Big Buckle Sandals | Sundance Catalog
BIRKENSTOCK – SHOES-n-FEET
Birkenstock Siena Big Buckle Narrow (Women) - Cognac Oiled Leather - The Heel Shoe Fitters