Joy, I was an early adopter and wear Rothy's most of the day, except when I'm wearing shoes kept at the office or boots in very cold weather, and I also wear them year-round as house shoes. I wash them about once a week, and find them very comfortable.
Although I have multiple pairs of the black round-toe flat that I rotate (and also have a few lighter shades and the slippers), I have only passed on two pairs that have worn out since I started wearing them about six years ago, and walk at least a mile in them most days.
As to sizing, a half-size up in the flats works best for me; however, I find some variation in the sizing even across the same size (that is, one shoe might feel tight, another shoe might feel like it is slipping off me). To ensure that I get the right fit, especially since I wear them so much, I tend to order three identical pairs, find the left and right shoe that fit best across the three pairs (not always in the same set!) and then send the other two back. They can shrink slightly with repeated washings, so when in doubt, I go with the version that is a touch looser. Since I only go through the exercise once a year at most, and shipping/returns are free and easy, it works out fine. Good luck!
