I have had my MS-20L for a year now. Still using the 6P3S-E outputs and 6J1P-EV in the front. Running the bias at .44 instead of .40, sounds better to me there. No issues at all with the tubes and I have no plans to change them, I even bought spares in case I blow some.
I am using Klipsch Heresy II speakers now, picked them up a month ago, upgraded the caps and plan to upgrade to the Heresy III woofers. The amp really sings with the Heresy's.
I use the UL mode pretty much all the time now, Triode just doesn't sound better with the new speakers and the UL mode has more punch. I also moved the 2 channel system into a larger room, it took a while to convince the wife.
I used to be an electronics tech in the 70s and love to tinker, thinking of replacing the coupling caps with Auricaps just to see if they make a difference, they are quite reasonable pricewise. I have changed a lot of crossover caps and found that more expensive does not always sound better. If I try it I will post the results here.
This amp is a keeper for sure.
The rest of the system:
Technics SL-1200M3D with Shure M97Xe cart
V-LPS phono pre-amp, I added a switch to adjust the input impedance and Pyramid power supply
Denon DCM-290 Cd changer
Klipsch Heresy II Signature Edition speakers
Not a great photo but it is hard to get everything in one shot.