question about Hague water softener, and replacement costs

Hello. I am having trouble with my Hague Maximizer Series 93 water
softener. It is working fine, despite being old, but the problem we
are having is that it is regenerating too frequently. It is supposed
to count down (the number being hundreds of gallons left before
regeneration) to zero, then regenerate, but it is counting down a few
hundred gallons (seems to be measuring the water use properly) then it
regenerates long before it ever reaches zero. The company that
installed it can't fix it.

What I want to know is, is there a way to tell it to NEVER regenerate
- we will make it regenerate at the appropriate time? In the manual it
seems like there are only two options - on demand, where it just
regenerates when it thinks it should, or delayed, where you set the
time that it should regenerate.

BTW, this is a residence, not a business - just a small townhouse. The
company that installed it can't figure out how to fix it, and wants us
to replace it - for $2300 installed. That seems insane, considering
that Sears has softeners for $500-$600 and will install for just over
$200. The company that gave us that estimate says the Sears units will
only last 2 or 3 years. That seems unlikely. It doesn't have to be
Sears - I can get a Waterboss 700 delivered to my local hardware store
for about $600 and hire a local plumber to install it. So what gives??