University of California Observatories has undertaken an effort to develop improved optical coatings for astronomy, with a particular emphasis on long-lived, highly efficient silver-based mirror coatings. We previously reported on a thin-film design including nickel oxide that showed significant improvement in accelerated aging tests, but had not yet undergone field testing. In this paper we briefly summarize our past work, and then discuss (a) two years’ field testing of our design with NiO; (b) efforts to find other materials that play the same role as NiO in improving durability; and (c) tests with ScF3 that show good results as a replacement for YF3/YbF3 but with improved optical properties. We also report on a long-term study of the effects of multiple cycles of stripping/re-coatings on various substrates, finding no significant substrate damage with aluminum, but some damage over time with our current protected-Ag coatings, particularly on borosilicate glass.