A softener that has stopped doing its job raises the same question each time: fix it or replace it. Age alone does not answer that. An old unit with good parts support can be cheaper to repair than a new one is to buy, while a unit with a cracked tank or a control that no longer has parts may not be worth touching. Set your ceiling before the quote arrives, so the repair number has something to be measured against.
What pushes the repair cost up
Parts availability is the first check. Ask the technician whether the exact control head, valve, or board is still made and stocked, and whether a substitute would need extra fittings or changes to the plumbing. A part that has to be ordered can mean a second visit, and a second visit is labor you pay for twice.
Tank condition is the second. A tank with a crack, a leak at a seam, or damage to the distributor needs replacement, and no valve repair fixes that. Resin condition matters too. If the resin also needs replacing, the repair line grows fast, so ask whether that work is included or quoted separately.
Number of trips is the third. A repair that needs a diagnosis visit, a parts order, and a return visit costs more than the part itself. Ask for the total labor on the quote, not just the hourly rate.
What keeps the repair cost down
Some faults are small. A cleaning, a loose fitting, a worn seal, or a single control part can be the whole job. Repair is clearly the better answer in these cases, as long as the tank and resin are sound and the control is still supported.
Set a ceiling before you ask for a quote
Write down three things before the technician arrives. First, what the unit still does for you, such as whether it softens enough water at the tap. Second, what you are willing to spend on a repair, given that the unit may be near the end of its working life. Third, what a full replacement quote would cost, with removal of the old unit, installation, and startup all included. If the repair estimate approaches the replacement figure, replacement often makes more sense, since a new unit comes with its own warranty, which you should read before you assume anything about it.
Questions to ask the technician
Ask whether the failure is in the control, the valve body, the tank, or the resin, and which of these the quote actually fixes. Ask whether the parts are in stock and how long a backorder would take. Ask what the repaired unit would still lack, such as a tank that is showing wear and may fail soon. Ask for the repair and replacement options on separate lines with the same scope, so you can compare them directly.
Repair or replacement is your call to make, and it is worth making on paper before the situation feels urgent, when the water tastes wrong and the choice seems to be forced on you.