Rotten Redwood Repair with Fix-it-all?

[Marshall Rousseau]

In the past I have repaired rotten siding and window trim with fix-it-all. The benefit is it can be sculpted to match the profile of difficult to find trim and can fix rotten patches of wood siding (up to a few inches in diameter) without pulling anything off the house. I did this a few years ago and it still looks good as new, but I recently read that its not recommended to use fix-it-all on the exterior of the home because it can absorb the moisture in the air and further rot the wood.  I would think as long as I prime and paint over it, it would keep the moisture out. Has anyone used this product 10+ years ago on outside wood repairs?  How has it held up? Are there any other products you would recommend instead? located in a wet area on the coast of northern California.