Hemorrhoids - how long do they survive cut off from blood supply

[radament1]

I had a hemorrhoid banding done  (had three, this was the last) 5 days ago. The band fell off with the first (effortless) bowel movement. My GP re-did it under warranty (pun intended), with double bands this time a day later (Double ligation on paper). However, today -so on the 4th day- i had a quite hard BM where i had to strain some. Not a lot, but certainly wasn't effortless. Im afraid now that it has fallen prematurely again.

So, on to my main topic. How long does a Hemorrhoid last once it has been banded before going necrotic? I know im probably fine, still, this was my last of the three, and i wanna make sure i AM reborn! :)

Thanks for the answers!