The financially correct way to do it would be to wait for it to plummet first before writing it off. So no, you don't want to get "ahead of the game" in the accounting sense.
So it depends if they're talking about a total write-off, or a write-off.
I think the misunderstanding comes from the fact that in everyday parlance, "write-off" often means a complete 100% loss (for example, my car was totaled, and it's a write-off). But in accounting, it does not.