Sex is not like vitamins. It doesn’t come with a recommended daily allowance. That being said, the most vocal complaint in marriages is that it is not enjoyed frequently enough.

The Bible commands sex in Christian marriages to be frequent enough that both individuals are satisfied, not just the spouse with the lower libido.

For the wife does not have authority over her own body, but the husband does. Likewise the husband does not have authority over his own body, but the wife does. Do not deprive one another, except perhaps by agreement for a limited time, that you may devote yourselves to prayer; but then come together again, so that Satan may not tempt you because of your lack of self-control. 1 Corinthians 7:4–5 (ESV)

One of the reasons many couples struggle with intimacy is because it is squeezed into an already full schedule. A wise couple plans romance and intimacy into their schedule and safeguards that time to guard heart and enrich their marriage.

Beyond the biblical teaching on this subject, studies indicate the average couple enjoys intimacy once to twice a week(1). These statistics span couples of all ages with younger couples enjoying intimacy much more frequently than older couples.

(1) http://www.marriagemissions.com/how-much-sex-is-normal/