Sildenafil and vardenafil have a shorter 4-6 hour active time frame. Tadalafil remains in the body longer, as long as 24-36 hours in most cases, and thus has a longer window of opportunity. For men that want to be able to have intercourse at any time, tadalafil might be the better choice. Sildenafil and vardenafil are prescribed for use as needed and might be a better option for individuals looking to plan a special occasion.