MRL Roller Lifter Street Durability

400lbs over the nose isn't terribly high, but it's a good amount. Your use will determine the life span. Highways and steady rpms wear things by putting heat into the parts. IMO, any solid roller build should have the bores bushed. Doing so means the longest expected life of the parts regardless of use. You should buy the best springs you can afford, potentially look into a beehive design that would do the same work with less pressure, and make sure there's a good flow of oil over them especially if extended rpms are expected. If it was me, I would want to check the spring pressures on all the springs yearly. I'm less concerned with the lifters as a lot has advanced over the past 10 years and if the springs are doing their job, the lifter's not being overly stressed.