My 2018 8-Speed Camry only has just under 7,000 miles. And over half of that has been highway driving. So I can't speak for longevity. But thus far it's been flawless as far as shifting. When it's cold, and going through it's first run up through the gears after backing out, it holds first and second a little long, then shifts abruptly. But the 8-Speed in my Jeep does the same thing. Once it cycles through the gears, and the fluid gets pumped through it, it shifts normally, and very smoothly.
The only thing I don't care for, is it really holds the gears to very high RPM if you stand on it. That can easily be eliminated by using the paddles. For me, I can't see the sense of revving an engine to almost red line. Others don't seem to mind. In high gear it loafs down the highway at just under 2,000 RPM at 75 MPH. Unless you watch the needle on the tachometer, you really can't tell when it's upshifting just driving around town.
To me it seems to be a bit smoother shifting than the 8-Speed in my Jeep. But you have to remember it's a rinky dink 4-cylinder, not a HEMI. I love it compared to the CVT equipped Corolla we first looked at. I couldn't stand the way it drove. The engine was revving all over the place. It felt like the worst slipping automatic in existence. Again, others don't seem to mind it. So if it keeps on going the way it has been, without any issues, I'm a happy camper. As always, time will tell.