My husband takes Naproxen regularly. Generally, he's been taking it per his rheumatologist's recommendation. It's similar to Motrin (another NSAID or nonsteroidal anti-inflammatory drug). It's what he calls, "Something to take the edge off." The benefit he found was that he didn't have to take as many pills in a day as Motrin. Sometimes he has to take a break with doctor's approval as it can irritate his stomach.
The idea is that this is a medication to reduce inflammation, which helps with my husband's AS symptoms, primarily pain and mobility.
Curious to hear whether it helps you at all!