Let’s say…
4x40 membrane costs $250
a carbon filter with auto backwash costs $1000
1-1/2 cuft of replacement AGC costs $150
Then, let’s say a chlorine fed membrane lives 2 years whereas a AGC filtered membrane will live 5 years. And, 1-1/2 cuft of AGC lasts about 5 years.
In 10 years…
Without the carbon filter:
5 membrane replacements: $250 x 5 = $1,250
Vs.
With the carbon filter:
1 AGC filter + 2 membrane replacements, + 1 AGC replacement: $1000 + $500 + $150 = $1,650
IMHO…there’s too much hand-wringing, hair pulling, and MATH to worry about it.
For a small, low volume wash I'd just replace the membrane with an inexpensive TFC and forget about the AGC.