Heres my situation: Been in current house in SE Michigan about 4 years. House has a Rheem Criterion 80+ furnace that is about 10 years old. AC compressor is a very old Carrier unit (I would guess about 20 years old). The compressor is old, rusted, and loud. The furnace seems to be in good shape, except that about 4 years ago the basement flooded and it was in 2 feet of water (over the circuit board but below the burner) for several hours. We had it checked by a large local contractor and they said it was fine. Heat and AC seem to be working fine at present. I know the AC needs to be replaced, but given the history on the furnace, should I consider replacing it at the same time? Would prices for AC be any less going into the cooler months than they would be in Spring? Thanks for your input.