The last two trips to the dermatologist led to some more treatments with liquid nitrogen, and some biopsies. All but one of the biopsies were clear, but the one, which was on a small area that felt like it had a metal shaving in it, revealed squamous cell carcinoma. Fortunately, the biopsy removed all of the cancer, so the next phase is to keep an eye on the area, and let the doctor know if something doesn't seem right.
The doctor prescribed a topical medication (Flourouracil) for the areas of keratosis the sun caused over the years of exposure. So far, it seems to be working, and over time, will remove the areas of damage. That's a good thing, because I was finding parts of my lower arms as ugly as homemade soap.
So, it continues. I pay for the foolishness of my youth, but have been lucky by not having dreaded Melanoma. Time will tell if I avoid this forever, but since I keep a close eye on my skin, even if I do, the chances of it becoming dangerous will be greatly reduced if caught early.