Just how bad can an Ion burn be?

[Gleb]

Originally Posted by Zenith26kc20

I guess I'm lucky with my 10 and 12 inch tubes

Yes you are, because the only thing responsible for ions is the quality and depth of the vacuum inside a CRT. That's why some straight-gun CRTs work for decades with no ion burn, while some others catch a horrible one in a year or two.
A fellow CRT rebuilder says that their shop has a very positive experience of rebuilding tubes with neither ion trap nor aluminizing. They use some modern, "very advanced" vacuum pumps, and ovenize CRTs very hard before evacuating.