If you know prior to graduate school that this is the path you want to take, you may opt for a program that offers gerontological counseling as a specialty. You will still be expected to take all the courses required for professional licensing in your state. However, your program will include a few electives like mental health counseling and assessment of older adults Your program won't necessarily be longer. Many states now require 60 units of graduate coursework, but they often allow some flexibility within this framework.
Another option, if you already have a license in a related field, is to pursue a graduate certificate in gerontological counseling. Your coursework may include offerings like psychopathology and aging and working as part of a geriatric care team. You may also get to choose electives like Alzheimer’s care.
I suppose it would be safe to say that gerontology counseling is coming of age, now that the Baby Boomers have begun to spill into their sixties.