Years ago when I built a log house, I researched what to use to treat the logs. Sikkens was a formula originating in one of the Scandanavian countries. It had been applied to wood buildings that were still preserved 600 years later. Sun is the worst for wood longevity. then moisture. It is the pigment in wood preservatives that protects from the sun. Therefore coatings like Thompson's have no protection in the sun. Wood needs to exhale also so it is kind of like the theory of gore tex. Block rain drops but be porous enough to let water vapor out.
I have been using Sikkens for 50 years and have never seen boring bees in anything I applied it too. It's not cheap, but it works. With all the laws limiting volatile chemicals, I would not be surprised if the original formula has been altered.
Just my observations, yours may vary.
Last year, I arranged to have my wrap around decks stained. I wanted to use Sikkens to match the house. No go. Apparently something was sold / bought regarding the Sikkens product line. Their "new" stain would not match my existing. The formulations and colors were different. Product ratings were not good either. I ended up using another product.
