I’m not sure what finish your paint is but you could protect your painted cabinets with a paste wax . Look up French furniture waxing it can be tedious but you could do it later if you find it’s wearing faster than you hoped. The poly coat can ruin your pain fob and leave it sticky. If you don’t know what your doing . It can also yellow the finish when exposed to sunlight and over time . I’d leave it for now and paste wax the finish later for a more durable finish. Just make sure you remove any dust particles prior to applying this method.