How long does it typically take a cancerous actinic keratosis to turn into cancer?

Months to years. Actinic keratosis is precancerous. The full transformation into skin cancer is a result of multiple number of relevant mutations that "tips" it over to become cancerous. Thus, if an actinic keratosis happens to have most of the mutations except one additional before it turns into skin cancer, it may only take a month of additional uv exposure before that happens.
Long time. Ak's can turn to cancer but it is a slow process, taking months to years. Keep your follow up as recommended by your md to keep an eye on them and make sure it doesn't progress to cancer.
Varies. Actinic keratosis are a sign of sun damage. It is prudent to treat the whole area with topical prescription creams such as effudex, sola raze gel.! orphotodynamictherapy. People with actinic damage need to be monitored because it is not possible to clinically distinguish between actinic keratosis, bowens, and squamous cell carcinoma.