Are my goats to old to learn??

I have 2 Nubian weathered weed eaters. They are 6yrs old. We have always done the T-post with heavy chain method for ease of changing locations. They have outgrown my physical strengths, and the new house is pretty much all slope. Aside from being drug down hills then having to drag them back up, they’ve cleared everything in zones 1-3. The hubby and I have entertained invisible fences or running a couple strands of hot wire. We have an active cougar and keeping them on 8’ chains is semi reminiscent of the goat at the beginning of Jurrasic Park. That said, having seen them demolish woven fencing in seconds, I’m skeptical on single strands. As it is now, they every so often find a way to unclip their chains( and inevitably destroy anything they know I love). I feel they aren’t the brightest bulbs, and it could be cruel to put hot wire out. I foresee them getting zapped over and over and over, and over again.
The price of chargers rated for goats is a little out of our means currently, but the transistor style may be an option. Will they eventually learn? Will they just bullhead their way thru the zaps? Will the shock frighten them making them stand-offish and hand shy. We have a love hate relationship most days. Most days I dream of poking them over and over with a cattle prod(evil laughs included)
Thanks

I don't see why they wouldn't be able to learn to an electric fence. I suspect many animals around my property are just as old (in comparison to the lifespan of their species) and they learn very quickly to leave my chickens alone, who are inside an electric fence.