ELEPHANT MOCK CHARGES - When do you need to make a definitive decision..?

Seen some interesting things in the bush in my short 53 years.Some friends and I kicked this question around a bit next to the fire over the week-end.Would like to hear some other views and opinions on Elephant mock charges.

Docman i had a few in my 18 years hunting full time. Buffalo, Elephant and lion. The worst was a non wounded male lion at my place. He did charge without any reason for that moment. He stopped at 15 yards growl and put up a hell of a show even scratched the ground with his back feet, flick his tail several times then turn around and walked away, i had him lined-up he was really at the end of my 375's barrel but shooting him was just not on for me. At that moment i was thinking if he go down to jump i will have to shoot but he was in a half sitting standing position all the time, at 15 yards i did not had much to play with. It then turned out that him and another male lion took down two Zebra very close by when i walked up on them. He was just guarding his meal. Well i made it out of the area and saved my skin.
Johan