Men love sex! But there is a basic problem all men suffer from that us lucky women don't... We can have multiple orgasms! Let's face it girls, after one orgasm all we want is another one. Men, however, are very different. Once they cum, they're done. Oh, it's not their fault. That's just the way they work. The key to giving a man more sexual pleasure than he is used to, is by denying him an orgasm. When his orgasm is denied, a man will be able to continue for as long as it takes to reach that much wanted release.
If you want your man to stay hard, deny him an orgasm and you will see what I mean. Here is the basic method for doing just that. You will need some basic supplies: A pair of rubber gloves (dish washing gloves work very well); Vegetable oil (it's much better and cheaper than commercial lubricants) or a cheap hand lotion.
You should tie him 'spread-eagle' if possible. You will want to have access to his perineum (the space between his balls and his anus). Once you have him securely bound. It's time to get started. Let's get one thing straight. He is NOT going to cum (if you can help it). At least not until you are ready to ride him to orgasm. Instead, he is going to be aroused to the point of exploding, but he will not be allowed to.
Now, put on one or both rubber gloves (both is better). Apply a liberal amount of oil to his cock, which should be hard by this time. If it isn't, simply put your mouth very close to it and breath heavily until your warm breath gets a reaction. Now, don't hold his cock in your fist. Instead, allow it to rest against your hand (fingers or palm) and very slowly slide your hand up and down his cock. He will love this! You should talk to him as much as you can. Tell him how big (or little if you want to humiliate him) his cock is. Tell him you know how good what you are doing must feel to him. Ask him if it feels good. Run your hand all over his oil soaked cock barely touching it. You don't want to allow him to cum so if he seems to be getting close, tell him he is not to cum until you give him permission.
You can rub your finger tips lightly up and down his perineum every so often. Ask how he likes that. Do the same to his balls. Continue teasing his cock, balls and perineum for as long as you like. If you even think he is getting close to cumming, stop! Don't touch him for several minutes. Continue talking to him, however. Ask if he was getting close to cumming. Ask him if he wants to cum. Tell him you are not ready for him to cum and that he needs to tell you if he thinks he is getting close to cumming. Remember, the objective is to tease his cock and balls until he is literally begging you to make him cum.
Continue doing all this for at least 30 minutes the first time (an hour is even better). When you are ready for a little attention yourself, release his cock and straddle his face so that he can orally please you. You can make him give you as many orgasms this way as you want. Don't touch his cock while he is pleasing you.
When you are satisfied that he has pleased you enough, you need to decide if you are going to allow him to cum or not. If you have never done this type of thing before, I recommend you allow it. You can mount him and ride him to orgasm or you can try something different. Untie one of his hands and order him to masturbate for you. If you have done your job right, he will be willing to do it. He should be so anxious to cum that he will do almost anything. Denying his orgasm altogether at this point will only make him irritated or even angry. So go ahead, decide how he will cum and make it happen.
In future sessions you can deny him an orgasm altogether. That would be a good time to introduce him to chastity. You can get a male chastity device at almost every online sex-toy store you can find. I would recommend starting with a plastic type such as one of the CB-X000 series (purely for economic reasons). You can move up to the more expensive (even custom) steel jobs later.
Once you have him all locked up, you'll see how much more loving he can be even out of the bedroom.