Viagra

Does anyone in this group have a SO that has to take Viagra? My husband just got prescribed it and he doesn't really have problems getting up, it's just keeping it up. I'm not one of those lady's that doesn't like going for hours, and I'm kinda worried it'll make him not orgasm as fast.. I want him fully hard, but I don't want him to last longer than an hour. What do y'all think?? What exactly does it do?