A couple might have many reasons for having sex every day of the month, but conceiving a child shouldn't necessarily be one of them.
In fact, when a man ejaculates frequently, his sperm count, sperm concentration and percentage of sperm that remain motile falls. Theoretically, this could reduce the semen's effectiveness.
Much more important than having sex every day (or multiple times a day) when trying to conceive is to have frequent sex during a woman's most fertile period, which, according to a study done by the New England Journal of medicine, is the six days immediately prior to ovulation. An easy way for a woman to predict impending ovulation is to use an at-home luteinizing hormone (LH) predictor kit. By urinating on the sticks provided in the kit, a surge in LH -- which occurs in the body approximately 24 to 36 hours before ovulation -- can be detected.