My recommendation as well, and you may still get some tax benefit based on the efficiency rating. We replaced our older Lennox about 5 years ago, for a new unit by Lennox.
Now I remember, we bought the house from the original owner at 15 years old. Add another 10 years and the heat exchanger of the Lennox unit failed two months just inside the warranty period!! Covered! We got $1,000 off the replacement unit. :-) How’s that for timing!