Hi Bill,
I had a Hi-Lux coating put on my 12 inch mirror by Orion Optics a few years ago and it is still in good condition. I haven’t examined it recent for pinholes but it still looks uniformly bright despite several years outside in the observatory. So I’m happy with it.
One thing that may be an issue is the reflectivity in the UV and IR, outside the ‘visible’ range. When doing spectroscopy I get the impression I’m not seeing as far into the UV or IR ends as I did when using just a plane old aluminium coating. I haven’t quantified this and it’s not really a significant problem but maybe something to investigate? I did contact Orion Optics to ask what the reflectivity was beyond their specified range of 400-700nm but the customer service person didn’t seem to understand the question(!).
Mike.