UV protection for deck stain besides sealer

Hi,

We stained a deck with Sikkens Cetol SRD a few years ago (from scratch), but the beautiful color became matte and looked very bad. The deck is in the sun a lot. A new coat will last 5 months tops. So, we just applied our new coat, but would like to retain the coat longer. Sikkens said that, because Cetol is a stain and sealer in 1, it's a bad idea to add a transparent UV sealer on top (since the sealer can't "soak" in) and could bladder off. Is that accurate? If so, are there any alternatives to a sealer to add UV protection for the deck?

Thank you!