echar una cana al aire 37
Although this phrase has no gender, it is more common to apply to a male. In principle would commit an infidelity, but extends to have a day (or night) of spree in the midst of a routine. A far-fetched origin is that males tend to prefer younger women feel younger when it comes to mislead our wives; and that compares with found a cane in the hair, start it, and throw it away to hide us over the years and believe that we are still young.