eddie shoestring, GlueBall,
Very well put. To sum it all, when we're flying in China, we're in the jungle, so expect the unexpected all the time.
Two things, though:
1 - For weather avoidance, as I said before, I only ask twice. After that I'm telling them where I'm turning.
2 - Concerning an emergency descent, if it happens to me (knock on wood) I will start it immediately.
And remember, a reasonable amount of extra fuel keeps your heartbeat at a normal rate and leaves room for several options when things start going south.