Couple things I did worked for me. I was topping off my sump directly from my RO/DI unit using a DC water solenoid valve to turn the RO water on when my sump dropped in the return chamber. This was causing lots of TDS creep exposure into the membrane with the constant on/off switching and exhausting the membrane really quickly, in turn exhausting the Di resin quickly. I now use a water storage container and a dosing pump to top off
The other was avoiding the regeneration on my home water softener. So, I force a regen before I make a large batch of water. At least 30 gallons at a time into my storage container for top-off, or my mixing container for salt water mixing.
Another is never let your softener run out of salt. I've made that mistake as well and blew out a membrane prematurely.
Hope that helps. I was super anxious to take on building and running CO2 Degassing chamber just to make RO water and so so glad I didn't have to do that