My understanding is they used to be fairly strict about using a set for 2 weeks before changing, but research has shown very little difference in outcomes down to 1 week.
There is some discomfort/soreness for the first few days after switching. My dentist's instructions were to wear each for at least a week and then switch to the next set whenever I wanted after that. Basically at whatever rate I was comfortable/could tolerate. I'm now at set 15 and have switched most of them after a week while a few I delayed a couple of days because I had something happening where I didn't want to worry about any discomfort.
There is some discomfort/soreness for the first few days after switching. My dentist's instructions were to wear each for at least a week and then switch to the next set whenever I wanted after that. Basically at whatever rate I was comfortable/could tolerate. I'm now at set 15 and have switched most of them after a week while a few I delayed a couple of days because I had something happening where I didn't want to worry about any discomfort.