Why not just change one and see if they sound different?
If they don't, then it is up to you to decide if the cost of replacing the second one is worth it.
Changing Tweeter on Olympica 3
Would like to get some opinions and advice. I wont be changing it myself, but for a 7 year old pair of Sonus Faber Olympica III’s , I need to replace the tweeter on one of the speakers. Is it strongly recommended to do both speakers? Or will it be ok sound wise by changing one (since the costs involved to change both).