I've had this slipper (in varying designs) numerous times now. I wear them daily for a few hours a day total. Always inside. Yet they fall apart within 3/4 months. I still keep buying them as they're cheap and comfy whilst they last. But if you're looking for longevity these definitely aren't the ones to go for!
I also always size up. I am a size 6 with slim feet and I buy a large. They feel tight when you first slide your foot in but quickly stretch out.