I know that if you are a woman, his loss of semen and orgasm might feel gratifying.
Some women experience that, others don't.
Now, your role as his Shakti or tantric sex partner is to help him reach this energy build up.
It won't happen if he loses semen.
Now, the heights you will reach in terms of love, union, complicity, spiritual connection are much higher if he does not lose semen and orgasm.
So, my advice is quite simple: help him.
For a guy it might be challenging to practice tantric sex if you try to push him to orgasm.
Instead, give him space. Don't focus on him coming.
Step back and let him relax when you feel he is about to reach his orgasm threshold.
Focus on energy build up instead.
There is no reason for him to come except for an instinctual response.
It is this response he wants to tame.
Help him! And get him to help you achieve the same!
You will be amazed of what happens when you do.
http://vitalcoaching.com/tantricsex.htm
To your tantric power
vitalcoach