I would never encourage anybody to bind longer than currently suggested time limits, or if there is discomfort.
That being said, I was measured for my binder in a shop by a pro, and other than having to learn how to squirm into the 997, I've had none of the discomfort others have experienced. No back pain, no rib pain, no trouble at all breathing (I would never stand for this), no rashes, just decent binding. It's a little more comfortable than a bra, physically, and way more mentally comfortable.
I'm generally binding 8 to 16 hours a day, no troubles. However, I will be having top surgery after binding for one year. So I will not have to deal with any effects from binding long term. If I didn't have plans for top surgery, and expected to be binding for years, I would definitely consider limiting binding time as much as possible, due to possible tissue damage.
Basically, a good measuring job and a good size chart, and a lucky body type (I
have large boobs and am somewhat fat, but have a short-ish torso) apparently can make a big difference.