Tempering Manuals

Hi all
Is there any advantage to learning the same tempering recipe multiple times? Does it improve the effect when you actually use that recipe to temper an item?

There’s 3 versions of each, lowest quality is blue, then yellow and finally the orange legendary. Once you’ve got the legendary version that’s it, it can’t be improved upon. If you find an identical manual and try to use it you should see a message saying recipe already learned.

OK. So duplicates are useless?
Thanks
That’s all i needed to know