The length of time it takes to paint a room varies, depending on a couple of factors. For example, the size of the job makes a difference. With a small bedroom, or with only a wall or two that have to be painted, the job can be done in half a day. Larger jobs take longer.
Also, if there are several different colors being used, the job may take longer, as one may have to dry before the other is applied. A 12-by-12 room with one color may take a morning. With multiple colors, the job may stretch into the afternoon.
Before you hire an interior painter near you, ask them how long it will take to paint the room(s) in your home.