What I mean is that they'll start sticking their heads through it(grass is always greener on the other side) and rubbing on it and before you know it a non-hot fence will be destroyed. Steers have a way of doing that. Ever seen a feedlot made out of cable? Guy here built one and the steers had the corner posts which were cemented in pulled out in only a couple years. Works similar on fence only they stretch the hell out of it. Plastic posts just aren't heavy enough at this point. If we could get some good heavy 5-6" plastic posts at a decent price then we'd be talking. Bring your skid steer or tractor and post pounder and you'll be on your top at the bottom of a lot of the hills. Last time we had a skid steer up there we wound up having to get a tractor to it. Any of the wood posts we've bought have come from the north. Only thing that seems to last is oak ties.

http://www.premier1supplies.com/detail.php?prod_id=484&cat_id=46 

These insulators seem to work well. We have one that wanted to come off because it was in too steep of a ravine. A piece of wire around the bottom of it seems to have stopped it. Other than that the only trouble we have with them coming loose is ocassionaly when a great white hunter desides he needs to chase deer on private property without permission. Really satisfied with the way our fences have worked out.