Would the wood decking receive added protection for a second coat of sealer applied several days later?

Thank you for taking the time to ask a question. The surface would be sealed and in order to be effective, this product should not be used over a sealed surface. To determine if the surface is sealed or can be sealed, perform a "Water Test". The water test is accomplished by dripping some water on the surface of the substrate. If the water penetrates into the surface and makes it noticeably darker, then it is ready for another coat of Semi-Transparent Stain. If the water beads up on the surface, then hold off on the application (currently the substrate is sealed and does not require an additional layer of sealer). If you have any other questions, please contact us directly at 1-877-825-7727 or info@cbgbrandreview.com. Sincerely, R.C., Digital Care Team