The well-meant advise on having tantric sex brings you actually further from your request. In tantra semen retention is valued, and ejaculation is supposed to be put to arrest. The younger and fit, the more ejaculations you're 'allowed' to have, but as a general rule of thumb you should not ejaculate more than a few times a year. Please note that this is only a side-issue as tantra is not about techniques but about spirituality.