Venus is easy to find because it is brilliant, outshining all the other planets and stars in the night sky. Only the moon is brighter. Since Venus alternates between being visible before sunrise and after sunset, it has been known from antiquity as both the Morning Star and the Evening Star.
How long is Venus visible? As the second planet from the sun, Venus can reach a much greater elongation (angular distance from the sun in our sky) than Mercury. So it can be visible for months at a time and hours each night.