It is always a good idea to have a few extra wires, so in the future,
if/when you get new equipment that may possibly require more wires (2
stage etc.) you will be ready. For a basic gas heat system, the minimum
is 4 between the thermostat and furnace and 2 between the furnace and
outside unit. There is 7wire made for sprinkler systems that will also
work for thermostat wire. Larry