Fast forward to yesterday and a different serviceman did the maintenance call. He spent about 30 minutes at the unit. I heard him cleaning coils etc. When he came back in, he told me that there were all kinds of things wrong and that we just needed to replace both the furnace and the A/C. He mentioned that the furnace is rusted (the previous guy didn't say a word about rust) and that the A/C is not in good shape. He then wanted me to schedule something right then to have a salesman come out and show me what deals they had. He also said the crawlspace is damp, but they could fix that for $3,900.
Call me a cynic, but it just didn't feel right. I thanked him and sent him on his way.
Maybe the units are on their last legs, but I'm not getting rid of them until they have breathed their last. And I think DH will be replacing the vapor barrier in the crawlspace on his vacation next month :)
Times like this, renting sounds awfully appealing ....