Calling Lamm ML2.1 owners

Thanks Syntax but my questions is how long before I replace new ones as they are on the amp for 10 years now. I have replaced the 6n6p many times already!

In terms of those 6c33c. I have brought a set from Thetubestore and worked fine. I read that they need to be carefully matched but lucky not so in my case. It seems as long as it is within range for correct bias to be set, it is fine. I know the regulation tube actually goes sooner than the power tube. Cheers.

I have a question about the 6c33c tubes? The tube store is marking them form 18 - 39 on the box. I wonder what that means and which should I be using for V1 and V2 position to get the best match?
Thanks.