I believe the best place for your blanket is near the item being dragged. The concept is that if the cable breaks it would normally be at the connection point so the blanket serves to absorb the snapping action. However I think if you have your cable extended far out and over rough terrain the blanket will probably pull off rather quickly. Of course if you have the blanket nearer to you then you can reposition it as needed and if the cable breaks well beyond that blanket point, the distance will likely absorb the snapping cable energy before it got near you. I really think the blanket is more logical for pulling something up close like a car on a trailer, etc. I would even say that a log with a short limb hooked over the cable a few feet back from the load might work as well for the log skidding application. The winch manual will give you the recommended location, my memory maybe faulty. And of course don't stand in line or too near the cable.
I also think that 15 minute rest period is for heavy strain on the winch. I doubt you will pull something that requires 15000lbs of winching capability, your tractor will be pulled backwards first IMO. If you are pulling a log that big you should probably cut it. Finally touching the winch motor early on in the process will tell you a bit about how hard it is working, don't wait until you have been using it for a long period, it might be extremely hot. Personally I like using one of those small laser infrared thermometers for checking the temperature of things, no finger touching and more accuracy. I use one to check my tires when driving on a long trip especially after a tire rotation or carrying a heavy load, etc. Comparing the temperature of the tires will tell you a lot about how well they are doing for the condition you are driving in.