Audio Aero Capitole - 6021W subminiature tube ??

I would appreciate hearing from someone who can explain the performance of these tubes in the Capitole, including the typical life of the tubes, whether they are susceptible to becomming microphonic or noisy, and how to purchase or change them if necessary. I believe I read these are really small (like the diameter of a pencil) and that they are soldered onto the board. If that is true, is it then necessary to send the player back to the distributor or manufacturer if they need replaced, or are these readily available and set up for user installation? How many years is typical for the tubes to perform in the Capitole before replacement is necessary? Thanks.
After all hassle appeared that Clayton's have been OK. And AA Cap finally died on me. There is no sound anymore, only quiet hum is coming out of both speakers. So I'm going to take advantage of my misfortune and upgrade it. I'm planning to replace Hovland Musicap with VCap CuTF caps, and Philips Jan 6021W with Sylvania . I have heard that Sylvania's are the best 6021W ? Is it much difference between plain Sylvania's and cryoed Sylvania ? Where can I buy cryoed Sylvania's, I'm having not luck finding them.
About my recent modification:
I have changed Musicaps in my AA Cap to VCap CuTF ($202). After 500 hours of burn in I have started my audition. I hoped that there would be any difference, to my surprise I have got real increase in transparent and resolution. But under the stipulation that AA was powered from AudioMagic Elipse. When powered directly from mains, differences are negligible. Now music is much more involving. Best upgrade I have done recently.
I was so excited about my "reasonably cheap" upgrade success, I decided to upgraded my Jan Philips 6021W stock tubes to cryo Sylvania 6021W.
Another 500 hours of burn in, and I have started my audition, no change in resolution, transparency, but I have lost bass impact and dynamics, I'm really frustrated.

How this could have happened, are not Sylvania's supposed to be better ?
Maybe Sylvania simply do not work well with VCap's ?
Did anybody tried Sylvania's in AA vs Philips ?
What were the results ?
I do not know what to do, pay technician to resoldier my old Philips, or maybe process of soldering tubes charged electrostatically AA board and I have to wait longer for it to discharge ...
You said in a previous post your AA Cap had died, what was wrong with it? Congratulations on the upgraded caps, where did you have the work done? Where did you get the cryo Sylvanias? I found several Sylvanias and I was going to get them cryod but I'm not sure it's worth the trouble. I think it was more of a way to sell an upgrade to reference.

Thanks in advance for any info you can give,
What was wrong, good question... nobody knows.
After months of fruitless repairs, appeared that he did not like my Legrand Power Strip to which my Audio Magic Eclipse was connected, AA was connected to Eclipse. I had to connect Eclipse to power strip which do not have any reactive elements, just the cheapest, simplest one I could buy. My AA is very finicky when it comes to power supply. It works from one socket at home and do not from another. I know it sounds crazy. I have asked electronics engineer about that, he was flabbergasted and could not explain it seeing it by himself.
Important now it works.

I get Sylvania's in Finland: Have sent them for cryo treatment to: (really cheap).

Do you know if in SE upgrade Philips or Sylvania 6021 W are used ?
I have the AA Cap Reference SE and my tubes are Philips, this does not mean the Philips sound better than the Sylvania, I think the Sylvania are just in short supply. I got some Sylvanias from Vacuum-Shop and another source from that part of the world. I contacted Tube World about getting mine Cryo treated but I'm just not sure it's worth it, Like I said, I think the Cryo might have been part of the selling point of the SE upgrade.