Would have hoped to get another year out of my HF-5 4040 but this one is ripe for the bin.
Have regularly replaced pre-filters, stuck closely to the filter replacement lifespan (40,000L) which works out about every 2 months for me. Daily 5-10 minute flushes before operation. TDS in is around 279ppm.
Thought it could have been the internal o rings failing, so replaced those but still very high TDS coming out, been like this for a little while now.
I would have imagined a softener would prolong the membrane life, but what's cheaper, replace it every 2 years, or put up with cost of re-gen salts and softener resin and hopefully get a bit more out the membrane......