Toyota Repair: 2007 Toyota 4 runner, 88,627 mileage, 4x4 actuator, high mileage

Question
With the last snow fall in St. Louis, I attempted to use my 4 wheel drive. Turned the knob to 4, watched for the lights to appear. Two images of car wheels show up on my control panel. One green and one yellow, both flashing. I turned back to 2 wheel, then back to 4 wheel and both indicator lights are flashing as before. I turned the car off. Waited. Restarted, and tried again still flashing both green and yellow. I continued to drive because the lights would not go off or quit flashing. Clearly I did not have the use of 4 wheel.
What causes this in a Toyota 4 runner? I have had several 4 wheel drive Toyota's with very high mileage and have never before experienced this. The Toyota service explained it was from - "little use". I would like to know where this is explained in the manual? Last winter, I may have used it twice. We had a mild winter. Is this unusual? Service rep. told me I can operate the car without it. So, Why do I need a Toyota 4 runner? This is the first time I have ever been disappointed with a Toyota.

Answer
The 4x4 actuator in the transfer case is probably stuck, this can happen from "little use" as they said, most dealers are knowleadgable enough to free the actuator up by tapping on the outside of the transfer case with a hammer, sometimes this works and sometimes not but they should give this a try.