I think that to equate less sex between married persons with asceticism is misguided, in my view this would not be a proper ascetical practice at all. It would seem that in marriage, barring any extenuating circumstances, it would only be natural for the couple to have marital relations on a fairly frequent basis, especially when they’re newlyweds. Naturally, with the arrival of children and the advancement of age they would probably have relations less frequently, but this would most likely be due to biological factors and quite simply being more tired more often due to the stresses of managing a family and work simultaneously. There isn’t any Church teaching that it is better for two married people to abstain from rathern than engage in procreative sexual relations in the interest of “asceticism.” In addition to carrying out God’s command to go forth and bear fruit, this activity between a husband and wife serves to bind them more closely together in authentic marital love.