Snape's timing.

[snailpower342]

No: HPFGUIDX 134946

Most of the evidence for Snape's motives have been thoroughly 
exhausted, but has anyone discussed the timing of Dumbledore's 
death? It could be said that this was the first moment in which 
Snape has come across Dumbledore so weak and vulnerable, but on page 
503 of HBP Dumbledore says:

"Had it not been...for my own prodigous skill, and Professor Snape's 
timely action when I returned to Hogwarts, desperately injured, I 
might not have lived to tell the tale."

This time Snape saves Dumbledore... Snape has had countless 
encounters with Dumbledore alone... why does he choose that one 
specific moment? Is it because he is surrounded by witnesses? Since 
Voldemort has ordered Draco to kill Dumbledore, he is obviously not 
looking for personal vengence. Snape could have killed Dumbledore 
any time for Voldemort's satisfaction. This time though, he will be 
given undeniable credit for Dumbledore's death by fellow Death 
Eaters...

Or is it the coinciding incident of Draco's failure? At this moment 
Snape only has two choices. Kill Dumbledore, or die himself. Even if 
this in no way proves Snape's allegience to Dumbledore, it does 
suggest that he waited until the last possible second. 

I am a firm believer in Dumbledore's trust, but I wondered what you 
all thought about this specific evidence. Have I missed anything? 

                          Niki and MFlo
           The Noble and Most Ancient House of Pancakes