I lived in a log home finished with the Cetol 1 and Cetol 23 Plus for over 15 years and can attest to the quality of the product. It does a great job. Our experience was that exposures that get little to no sun will easily go 2-3 years without a re-coat. The sunny exposures are 1-2 years. In both cases, make sure the area is clean, remove any loose Cetol (usually none) and recoat with Cetol 23 Plus. If for some reason there is a spot down to bare wood, coat with the Cetol 1 first, and then re-coat with the Cetol 23 Pus. The main thing is to follow the instructions are to number of coats.