I can't yet tell you how they will last but I just replaced all 8 windows on my '81 Yamaha 30 - just DC 795 surface mount - no fasteners. I followed the advice posted by Maine Sail here (WTH!!!!!!! Silicone problem..
) and followed the Dow Corning data sheet for DC 795. I purchased the 795 from my local glass shop as none of the marine stores in the area sell it. (!)
I was deterred from using SikaFlex 295UV by the data sheet recommendation that the joint be masked from sunlight to prevent degradation from UV.
I used rubber washers as spacers to ensure I had the bead thickness recommended for my window dimensions (6-8mm). DC 795 is cheap (<$10) for a 300 mL tube. Which is good because I used 20! I tried to get cast acrylic but in my tint it is apparently a custom run. My plastic supplier lead me to believe he had sourced it but when I unpacked the windows at the boat the material designation was for extruded. I complained but went ahead and installed it. I have 1 more week of curing to wait...then in a month, year, or a decade I will know how it worked!