I'm pretty sure I read somewhere that Motorola made some later 23EGP22's themselves after the bad experience with NVC, and that they were much more reliable.

NVC did go bankrupt and out of business in I think 1969. I believe the 23EG was the only color tube they made. Supposedly their B&W's were still ok, but by the late 60's most OEM's had gone overseas for B&W and nobody wanted them to make color ones.