1 Corinthians 7:5
Defraud ye not one the other, except [it be] with consent for a time, that ye may give yourselves to fasting and prayer; and come together again, that Satan tempt you not for your incontinency.
Note 7 at 1Co 7:5: The Greek word that was translated "defraud" here is "APOSTEREO," and it "signifies to rob, despoil, defraud" (Vine's Expository Dictionary). This is a continuation of the point Paul started making in 1Co 7:3. Within marriage, one partner does not have the right to withhold normal sexual relationships from his or her mate. Here Paul gave the guidelines for the only exception to this instruction.
To withdraw sexually from marriage, there must be mutual consent for a limited period of time for the express purpose of seeking God through fasting and prayer. No other exceptions are given.
The fact that fasting is involved during this time of separation means that this is a relatively short period of time. Any couple who has stopped sexual relationships for extended periods of time is not functioning in a healthy physical relationship.
Note 8 at 1Co 7:5: The word "incontinency" in the Greek means "want of self-restraint" (Strong's Concordance). Instead of Paul telling the individuals to get their desires in line, he commanded the sexual relationship to resume so that the temptation would be diminished. The answer to sexual immorality is not unlimited relations within marriage, but infrequency of relations within marriage is a temptation that Paul commanded couples to avoid.