I use 4 strands of 1/4" thick white poly rope with 9 strands of wire woven through it. We use screw in plastic insulators on treated wood posts and electrify the top and third strands down. We put the fence aroound two large paddocks that are about 3-4 acres each, two years ago. It has been through two winters where temps get into the -40s and the snow was over 2 feet deep. It has also been through hot summers where temps get in the high 80s with frequent heavy wind and thunder showers. We had golf ball sized hail in a storm earlier this week. So far, the fence has weathered well, looks really good and I've had no problems with it losing conductability. My horses have never challenged it. They seem to see it just fine and know exactly how close they can get to it.
I do walk the fence line about once a week to check it and have only had two minor issues. In one location, the poly has frayed ever so slightly. I wrapped a small piece of duct tape around it to prevent it from getting worse, but don't think I needed to. Maybe 3 strands of the poly separated. I also have to adjust the tension on the fence a couple times a year. In colder weather it seems to stretch and tighten when it warms up. I tighten it in about December, before the really cold weather hits and loosen a bit in about May.