I'd say that although Viagra can give you some serious wood. I've had users tell me they get a massive headache from it the next day.
Whats wrong with just using what you've got, after having added some to it with Penis Enlargement for six months or more. He he he
Girls aren't stupid, if they notice a 4 hour erection they know whats up.
Besides if you lose your erection after you cum just have her suck it for a few seconds, it'll be back in shape in no time. And if it takes longer, well you just got a blow job, so quit complainin'.