Sex drive does decline with age. This all depends on how the person takes care of themselves as they age. I think many couples still have a sex drive as they get older, even if it is not as strong as it once was. I think sex drive all depends on your health.
Research consistently suggests that sex drive declines with age for both physiological and psychological reasons. The sex drive is primarily driven by the desire to procreate. As people mature beyond child bearing years, they feel less compelled to have sex. Also, as people mature, they find satisfaction in other areas of life and feel less of a need to have sex. There also becomes a point the lives of some people at which sex is unsafe.