Holding My Breath My AC Keeps Working

At my condo building, my AC unit is the oldest. When you go outside and look at my rheem heat pump, you can tell it is the oldest. I have had some close calls in the last couple of years, but it has always gotten fixed. Thank goodness! I just can't afford to buy a new one right now. I don't know when I can, so I keep hoping it chugs along. And it does. I know I will have to shell out some money at some point for a new system, but why fix what isn't broken for long?