I get Sildenafil on prescription 100mg as the 50mg doesn't work very well on me (well I am over 60 so I need it). The Dr won't give me the branded Viagra as he says sildenafil is just the same - but I am convinced it's better if only he would give it to me. It's a cost thing as Viagra obviously costs the NHS more. But of course it could just be a psychological thing that I believe it to be!
I don't seem why you can't pop twice on Viagra as it is supposed to last a while (up to about 5 hours) so certainly if you have the ability to pop twice in half an hours or then go for it. The maximal length of an erection whilst taking Viagra is supposed to be about 30 mins. I find that if I don't pop within 15 - 20 mins my erection start to wear off and so does the ability to pop, but everyone is different depending on their personal body chemistery. Through personal experience I completely lose the urge once I have had one pop, don't know if its the pill or whether its just my age - I guess the latter is the case.
You should take the pill about 30 mins before you want sex so generally I take it as a set to get to my punt (never more than half an hour away) - off course the issue is if one does't turn up or it goes wrong then unless I have a plan B around the corner then the pill is wasted as after an hour, I'm past the peak. The hardest point of the erection is supposed to be about 1hr after taking it so after that its' down hill. Some men can off course still get an erection upto 12 hours or more after taking it .
I have also used the other one Cialis which is supposed to work much quicker like in 15 mins and it is supposed to last longer - so good for those sexually active men who have a partner who still wants it every day!!! It didn't work very well on my at all.
By the way, you should never have a big meal and then take Viagra expecting it to work as it won't work on a full stomach. So don't go for a meal with your punt or other half and then expect to get down to it when you get home as you may be disspointed. Take her for a meal afterwards! I had a very embarrasing experience when I first started punting and taking Viagra as I didn't know about the food warning. I went for a meal with a friend and afterwards I had a punt lined up with the gorgous and sexy wg - who I guess most of you on here will have shagged. She did everything she could to make me hard and despite taking the little blue pill I just couldn't get an erection - so embarrassing. Needless to say, I had a return session with her two weeks later on an empty stomach and gave her a right old fucking!!