If cost of repairs is 50% of what the new equipment costs, then new equipment is the best choice. Band aiding your system can add years to its life, but too many band aids and you could have going a new system.
Your old equipment out of warranty? Getting new equipment means getting new manufacturing warranty's giving your comfort peace of mind.
with a investment in new equipment, for your home, gives you better energy efficiency. That efficiency saves to money on your electric bill. That money saved is a rate of return on the investment of the new equipment. The rate of return will pay for the new equipment over so many years. Win, win.