I certainly wouldn't lose any sleep over having ONLY 8 rounds of .357 magnum. Sure there could be a situation where that's not enough. Of course there is a situation where a Glock 17 with several 33 round magazines wouldn't be enough. Think how many people are out there with less than 8 rounds of 9mm, .40 or .45. Heck, think of how many are out there with absolutely nothing! Get proficient with it and I think you are about as prepared as you need to be realistically.
"I have sworn upon the altar of God eternal hostility against every form of tyranny over the mind of man."