You may get multiple erections during this time, but an erection should never last longer than four hours. Viagra will last at least four hours and as long as 12 hours in some individuals. It can be dangerous to take sildenafil if you also take medicines called nitrates often given for chest pain. This time may be as short as a few minutes in younger people and as long as a few hours or days in older adults. When ED can come with so many frustrations and psychological difficulties to begin with, taking a treatment that you know will actually work is your best option. · When they’re still perfectly new and efficient, Viagra actually lasts as long as two hours. Of course, this would vary depending on your health and metabolism, but that’s the estimated length. Some can even last as long as four hours. On average, the effects of Viagra would peak at the first hour, so if you’re using it for ED, then this. The official Viagra shelf life is two years, but this isn’t true across the board for generic unbranded Sildenafil providers – because some have differing shelf lives. However, this is only the period in which Viagra can be guaranteed to remain as effective and safe as intended. Depending on storage conditions, Sildenafil may remain. Cialis: 7 Important Things to Know Does Cialis lower blood pressure? Do you know these 11 amazing facts about Viagra? How long does Viagra last and how soon does it work? .