I'm not sure why a water softener would be hard on an RO/DI unit. I've had my first one for about a year, and I just replaced the DI resin. It's been hooked up to my icemaker too - classic on/off cycling. I still had nearly 0 tds when I replaced it. I pay $10 a bag for the resin. Also remember that SOME manufacturers (Coralife) don't use the expensive (correct) resin.