Hey Tom,
Great to see someone else here with the G5 L4.
I've had mine for just over 2 months. You can expect it to continue "blooming" for a couple of hundred hours use, though I think most change occurs within 100 Hours and then gradually tapers.
My unit came with the a GE 6X5, RFT 12AU7/ECC82, plus Amperex PQ 6DJ8 - a very fine set of tubes, indeed.
I've found it impossible to better the RFT. They bested all of my faves. I did replace the Amperx 6DJ8, not because they did not sound very good but to sharpen up my system's sound with a pair of Seimens.
Today I turned the system on after about 4 or 5 days of letting things rest - it's been on way more than off for these two months. I'm amazed every time I hear the system and music with the Lampi - more amazed that my old CD's (now ripped to hard drive) can sound do good!
I admit that for quite a while I had been a "vinyl supremist" and "digital derider."
That sure has change dramatically as of late. My turntable and records must think I have passed away.

I have a couple of more things planned that I expect will make it better still. As of now the music has a solidity and 3D effect that I've never heard before - certainly not not from digital.
So enjoy Tom, and know that it's just going to get better and better.
Doak