Dear luis16Like most things in life, this is a gradual change. Your cartilages continue to grow and that becomes more noticeable as we age. there is no set age. Very often, it becomes noticeable in late 60s and forward. This usually applies to nasal tip and ears.
The nose tends to age by thinning of the skin and weakening the ligaments connecting the nasal cartilages. When patient's have an Active depressor septi ligament, every time they smile it pulls the tip down which further weakens the droopiness over decades.