For my first time trying it, I chose to read the instructions and follow it. It told me to boil how water and stick the trays in the water for 90 seconds. I timed it on my phone and before the 90 seconds was up my teeth tray was so shriveled up that I had to throw it out and use a new one. I think maybe it would be good for like 50 seconds. If it ends up working I’ll buy more.