O Ring Lifespan

After nearly two years under pressure the o rings on my Marauder gauge block have begun leaking down. I replaced them back when I was tuning because the sharp openings in the air tube had clipped them. I sanded the sharp edges down and was leak free for nearly two years. My question is what is the expected life span of o rings under constant 2500 - 3000 PSI? Think I will add an aftermarket depinger and SSG while Im in there.