I'm not at the age where i need these things yet but I did experiment with some over the counter pills at times when my erection was affected due to stress. I tried them a couple of times and while they did get the job done and kept me hard, every time I took them I would get a headache, so I stopped. I can attest that the best way to prevent ED is regular exercise. As a guy who works out, I can testify that the better shape you are, the more good sex feels. When I experimented with the pills, it kept me hard but that's it. Working out and being in great shape also enhances not just the erection , but the sensation and pleasure.