There is never an easy choice of whether to replace or repair HVAC and heating components. These notes will give you a better picture of what's in the future for your equipment.
Consult the Service Notes
Hopefully, you have kept a log of when service visits were done on your equipment. Your current heating contractor might want to see these to determine what kinds of problems have already surfaced with the equipment. They can also get a better idea of whether the service schedule you've kept matches what the equipment needs. Too infrequent service will wear down the machine and may lead your contractor to recommend replacement sooner rather than later.
Here are some examples of how maintenance and repairs will affect the lifespan of the system. Consider two HVAC systems, one that's had yearly cleanings and one that hasn't been serviced since it broke down 3 years ago. The first system is going to last much longer. When cleaning doesn't take place, the heating system has to work harder to churn out heated air despite having impurities in its combustion chamber and despite the air filter being clogged.
It also matters whether the repairs done were short-term repairs or fixes that were geared to last long-term. If you replace a smaller part to compensate for a larger part that's not working right, the problem will eventually catch up to you when the system is overtaxed and burns out early.
Look at the Life Expectancy
Within the user manual of your devices, you should find the expected life expectancy of your heater and/or HVAC components. If you're on the long side of that recommendation, it could cost you less to simply replace the equipment rather than deal with the more frequent maintenance needs that may come up in the future.
Look at Efficiency
You can also look at efficiency as a measure of whether or not to replace the equipment. First, estimate how much energy the appliance is using on a yearly basis now. Then, get your heating contractor to estimate how much more efficient it would be with repairs. The system probably won't rival a new heating and HVAC installation still, since all systems lose efficiency over time. Compare your numbers to the performance of a new installation. You're somewhere on the scale from efficient to inefficient, and if you're at the bottom of that scale, it might be better to replace your equipment now and reap those years of energy savings.
