Aging System

Past ten or twelve years a system starts telling you what it is going to cost: a repair that would have been routine at year five, a bill creeping up, a house that takes longer to recover on a hot afternoon. None of that on its own means replace it. What decides it is the cost of the next repair set against the life left in the equipment — and whether the refrigerant it runs on is still being produced, because that is what makes a leak expensive rather than routine.