How many Proofs of Legend do I need?

Hello

I was wondering how much make sense to farm. I figured I need 5 for the Proof of Triumph (which I can share across characters) and then 5 for each character, so that everyone has the Anniversary weapon.

I think the decade weapons are not really worth it, as the 5% dmg increase a few times of the year does not justify carrying them around.

Also the blessings of war or not worth farming them for.

Are there case where one would need more than one anniversary weapon or are there other reasons to get more Proofs of Legend?

Thanks!