We had a water system installed several years ago, and it did a great job. However, the iron problem we had is back. This is an Iron Boss that supposedly had much capacity to spare. I've used Iron Out and backwashed it repeatedly, but it seems it's worn out. It's been serviced, and the tech says it's perfectly fine. I don't think our well water has changed all that much. What's the life expectancy for an iron filter? Should it be replaced?