Mine look a bit ratty, right? Thats because Ive been wearing them about 360 days a year for the last 7 years (I work from home, so I mean ALL day). I get new insoles once a year. My slippers are a size 8, so I buy size 8 UGG insoles. I slide the new insole in and secure it under the heel section with a piece of folded over duct tape. It holds all year. Best slippers ever. Ill never go without them if I can help it.

Note that these slippers run large compared to UGG boots. I wear an 8 in the slippers and a 9 Im the classic boots.