I never thought about using WD40 for long term waterproofing. Wouldn’t it get messy from reapplying and collecting dust?
I use: T9 Boeshield on all my motorcycle parts that I don’t want to rust. I just googled it and seems like it’s acceptable for ignitions. It’s waxy, so still collects dirt and stuff. But, it’s a one time application.
On this side of the pond, WD40 is an expensive exotic import. If someone is gonna shell out the cash, might as well last a while.