Rebuilt 15GP22's?

[frenchy]

<<<I always thought that the phosphors in black and white tubes degraded with use too. >>>

Since back then there were no news channel crawls, logos, videogames etc. it would have been evenly worn as long as the set was working right. I can see if something went wrong like you lost vertical for hours while nobody was tending to the set and it burned a horizontal line into the phosphors. Or the ion trap got messed up and it ended up causing a burn spot in the center.
Otherwise the big % of the cause of dimness in an old tube is probably the gun's fault or because of outgassing. Plus doing the guns is hard enough, I can imagine the pain it might be to remove/replace the phosphors. How was that done anyway? Or did they even do it?