Kaibee:
Your SWG will not stop working unless you run it over night and will provide you a warning. This has never happened to me during the day, even towards the end of October. Unfortunately these NJ temperatures have not been cooperating for anyone. It is better to maintain the heat, unless your heater is so fast that you can bring up the temperature 10* in 24 hours.
A solar cover is huge. I have not been home, but have 85% of the pool covered in a blue 12 mil cover and this morning, the internal temperature was still 84*. The heat probably runs 4 hours daily, as the timer is only on for 6 hours. Yesterday was a very humid day as well helping out with the temperatures.
The best thing to do with a solar cover is to cut in half or even 3 parts. Overlap by about 1' for the middle piece on each side. This will help retain heat during times like this. Solar covers work to retain heat, but can be a PIA to take off and put on, but the alternative is to run the heater all the time wasting a lot of gas.