All of the reading I have done on DC tubes have stated their run life is much shorter than a RF tube for engraving. Agree the cheap china tubes are the shortest of the bunch. But even on the US made tubes the longest life I have seen advertised is 5k hours. On the other hand the RF tubes are rated for 45K+ hours. Example RF head:
25W CO2 laser with proven operating lifetimes of more than 45,000 hours, only from Synrad the worlds leading manufacturer of sealed CO2 lasers So based on mfg data no BS there. Now like I said if your not doing daily heavy use the cost advantages of a DC tube may well outweigh the operating hours of a RF. Both types of tubes degas over time so even if it just sits on a shelf and is not being used the clock is ticking and more than likely will not work after 5 to 10 years.
If you have a link to a 10K+ HVDC tube please pass it along getting close to the point were I need to start thinking about buying the laser head.