American scholars summed up a "love frequency formula" according to the influence law of age factors on ability-love frequency = ten digits of age' 9. The ten digits of the product are time, and the single digits are the times that should be in this period. For example, for men in their thirties, 3'9=27, which should be 7 times every 20 days, about once every three days, without affecting their health and working conditions. This formula applies to adults over 30 years old (as follows).
Over 30 years old, 3X9=27, that is, 7 times every 20 days (once every 3 days).
Over 40 years old, 4X9=36, that is, 6 times every 30 days (once every 5 days).
Over 50 years old, 5X9=45, that is, 5 times every 40 days (once every 8 days).
Over 60 years old, 6X9=54, that is, 4 times every 50 days (/kloc-once every 0/2 days).