There are a few points to consider. You save some money on labor by changing out all the equipment at the same time. If you change the furnaces later, then you may have to disconnect the coils from the furnace. This adds additional labor and refrigerant charges. Depending on how many years it is from now, you may not be able to find an AHRI approved match with the new furnace and the condensers you are putting in now. If you keep the current furnaces then you are restricted to getting single stage AC condensers. A 2-stage condenser will require a variable speed furnace. Finally some manufacturers offer better rebates when you purchase the furnace and AC at the same time. In addition if you move up to 95%+ efficiency furnace you may qualify for a local utility rebate. The sum of these additional rebates help offset the cost of the furnaces.

one other question ... when i set my Fan on AUTO ... the fan runs for about 1 to 2 minutes after the compressor shuts off ... just long enough to increase the RH in my ducts to a humid 75% before shutting off the airflow ... Is there a way to tweak the electronics so that the fan actually completely shuts down exactly when the compressor shuts off? That would keep the air in my ductwork a dry and mold inhibiting RH of 45% Thanks for any ideas

Is this an Carrier Infinity AC? Do you have an Infinity controller? If yes have you look at the faults listed in the controller? If the compressor is less than 10 years old it may be covered under the parts warranty. It is possible to run the AC in the high stage only. But I think this is the start of more problems. I suggest you have it serviced to determine what needs to be fixed.

In the case of the Mitsubishi mini split you stated in an earlier post that a second contractor would not want to get involved in a warranty repair. But in the case of a Goodman condenser you take on a warranty repair job (let's assume it is a 410a refrigerant) with no hesitation. This seems like a contraction. Can you explain what is different in these two situations? Mike good question. I can tell you it's a somewhat complicated answer. In business the goal is profitability whether you like this or not it's the only reason you go to work so it's no different for me. How I get paid is what I collect from you the home owner I am doing work for. After deducting a lot of expenses what is left over at the end of the year is what I pay myself. There are no two years alike. Just because you have a good year or two, doesn't mean it will continue. So aside from that you have statistics. How likely am I to find a Goodman condenser that needs repair? Simple odds tells me very likely. A mini split? not so likely. On a good day they may make up 5% of the market maybe even less than this in my area. Doesn't it make good business sense to be a repair specialist for the Goodman condenser ( I work on all HVAC brands so I use the term Goodman, loosely here.) Special tools and procedures are required to work on mini splits not to mention having to continually train and update as the technology progresses only to serve at best a 5% market size. It doesn't mean I wouldn't work on a mini split, but someone calling me about a system I didn't install in the mini split market category is going to pay me to learn their system not to mention buy the tools required to work on it, because I am not going to waste my time trying to keep up to date on a market segment that makes up 5% of my market. On top of this many mini split manufacturer's market their systems to the DIY crowd. I have no interest in running down this rabbit hole with you. You know I give an estimate to repair and the guy says 'Hey, I bought this whole system for $600 five years ago and put it in myself.' My response to that is: then why are you calling me? I guess because it's easier to pick up a phone. There's simple for you on a platter.