I am in the process of painting my front porch. I primed with Sherwin Williams Loxon Concrete and Masonry primer, then used Behr's Porch and Patio Floor paint. While Sherwin Williams told me that I won't need to apply a sealant, I'm also planning on a decorative finish (using a high gloss of a slightly darker color to create a design) and want the porch to last a few seasons before I have to repaint. The porch is covered, but still gets wet during rain and also accumulates snow during the winter. Should I seal it when complete, and, if so, what product should I use to extend the life of the paint job?