Why not just use wood posts with steel tee posts in between the wood posts.  I have very rough up and down terrain, the wood posts are about 60 ft apart with 5 or 6 steel tee posts about 10 ft apart on a high tensile fence. Use the black insulators on the middle wire which is hot.

People keep posting about the hot wire shorting out to the tee posts but I have not seen that where smooth high tensile wire is used.  The first fence a local contractor put up for me he used barb wire on all wires including the middle one which I told him I wanted to be hot. There the tips of the barbs did short out around the insulators to the tee posts when the weather was damp until I went all the way around with a pair of pliers on the barbs. But that was the contractors issue, not the tee posts. The hot wire should always be smooth high tensile.

On all later fences, both 4 barb/1 smooth and all smooth high tensile, I have never had a problem with shorts. I'm pretty sure that in my up and down terrain it is not a good idea to space posts very far apart, especially with high tensile and the high tension forces trying to pull posts out in the low spots or bend the posts over on the high spots.

We usually expect a permanent perimeter fence to last a long time. Well worth doing it right the first time. So much of the cost of a fence (50%+?) is in the labor it pays to do it right, for your terrain and use, the first time.

One key may be to use good UV stabilized insulators the first time. I've had good luck with the Dare black tee post and wood post insulators.

I had a disaster with Gallagher white insulators a few years ago. Not enough UV stabilizer and every one of those got brittle and failed within a couple years. A very expensive lesson and strongly suggest folks to avoid Gallagher insulators. My local dealer still sells their chargers (which I like) but not their insulators.