Being a former Writer/Editor
of "Vacuum Tube Valley (get it? hint: it started in Sunnyvale CA) Magazine: Celebrating the History & Technology of Vacuum Tube Technology"
http://www.vacuumtube.com ...we know a little about this subject. Unfortunately, Owner/Publisher Charlie Kittleson died a few years ago at age 60, so VTV went out of publication, no one else involved had the capital to ensure continuation; an internet spin-off by the VTV Tech Editor
http://wwwclarisonus.com survives. VTV would have succumbed anyway, at some point, as all small specialty print publications are now highly endangered.
In any event, French guy's craftsmanship is impeccable. However it is literally impossible for him to create tubes of the highest quality for 3 main reasons... 1.It's not likely for him to have the kind of evacuation equipment to get vacuum hardness to the best level possible. This has effect on reliability/longevity. 2. And of greater import is that some of the materials, specifically the exotic military grade layered strategic metals used as cathode materials, German ultra-pure nickel, superior reagent grade chemicals for cathode coating, etc etc just can no longer be obtained. Some of them were specially made for WE,RCA,GE, Philips, GEC, Amperex etc. and with the demise of the high volume tube industry into what is now a boutique product, manufacture of such ultra quality components could no longer be justified and are not available at any price . The problem will become even greater, and soon, with the recent demise of high volume CRT tube production for use in TVs. Use of gold plated control grids, precision spacing of grid to cathode, grid spacing and geometry, all are impossible for the boutique maker to accomplish to the degree formerly possible in the 1960s. Big Russian and Chinese factories from the Cold war era never went out of business and are now making 90% of current production tubes, mostly for the guitar market (about 95% of the market), and some of them never had this technology or materials to start with, even back in the day. Richardson and some super-specialists still make Eimac and other highly esoteric Military-transmitting-Radar tubes in the US, but that's about it, and I'm not sure even those are what they were 30 yrs ago. The new "WE" re-issue 300Bs and such are the best new tubes made for consumer but still not as good as '60s vintage. 3. He cannot have the burn-in and testing regimen needed to ensure highest quality, hugely expensive. At it's best mfr's had a significant % of clunkers that had to be weeded out. All this said, however, we're lucky that ANY new tubes are still being made, and more power to the Monsieur in France for his admirable work...Formidable! We collect/trade/restore vintage vacuum tube equipment, and it's good to know that these kind of skills and techniques are being preserved.