Our deck is large–over 500 ft. We power washed and then treated with a product like Thompson’s deck sealant. We have to do this every two years. Will anything else last longer? I wonder about using regular exterior house paint. FYI the deck is in the sun all day.
It's your choice of product. I'm not a fan of Thompson's deck products. The key is to use a stain with more pigment. I like Cabot's semi-solid decking stains. They do last longer and offer easier maintenance in long run. Refer to <a href="https://www.house-painting-info.com/deck-stain.html">Choosing a Deck Stain</a> for more information.
Don't use regular house paint. It isn't designed for horizontal surfaces and will peel in a short amount of time.