I've been using wheel bearing grease. Got a can for $6. Should last most, if not all of my lifetime.
I use high temp, high friction grease that comes in a tube. 3 dollars for a big tube and it only takes a finger tip of the stuff to coat my AK. Cleaned my AK, applied this and even after all the rapid firing and just letting it sit the grease held up fantastically! Even when I finally got to cleaning my AK, it was an experiment, there was still a very fine layer of grease on the parts. The stuff is red, but after catching carbon it turns black, go figure lol, and just keeps on pluggin. Great stuff, and I use it on my Glock too.