The deep-fried spoons are described by Picken in his 1975 book, with some theorizing about the physics behind it. He doesn't suggest it was a new idea at the time, so it looks like they go back a few decades at least, and since some of the ways they are used are rather elaborate, more likely a lot longer.

Julian Goodacre's workshop has an oil heater for treating pieces of bagpipe, and I asked him if he was using the deep-frying technique. He said no, but other makers of wind instruments did.