The phrase "several hours" means a duration of time that is more than one hour but less than ten or twenty. It can vary depending on the context, and it usually refers to an extended period of time during which something happens or occurs.
I would leave it for several hours of course in the pans before placing into the heated oven. (artisanbreadinfive.com)
It initially seems to be as nuanced as the basic riding mechanics, but even after several hours of play, I was never able to get a handle on specifics. (snackbar-games.com)
Women have extremely busy daily schedules, and the idea of spending several hours in the gym seems impossible. (homefitnessguru.net)