A:Answer The time is a preset 15 min, though you can just restart another session if you want. The paperwork does suggest doing only 30 min (two sessions of 15 min each) maximum at a time. During that 15 min you can adjust the power, or change the type/location, like if you start on "knead" you can change to "back" if you want. They do feel a little different, so you might prefer one over another, ie, maybe "foot" feels better on your back to you than "back" does. Definitely try all those and just use what feels best.