I've got 4-conductor cable now, but am looking to put in a smart thermostat (ecobee3). It requires a C wire, or the use of their adapter kit, so I'm thinking of just pulling new cable.
7-conductor is obviously cheaper than 8, but I also realize the cost difference is neglible in the long run. I've got single stage heat and cool, and a fan, so 4 wires have served well until now. I could maybe forsee adding a (de)humidifier in the future, but don't think I would ever install anything else (furnace and AC were replaced 2 years ago), rendering the extra wires redundant.
Will I be severely hampering upgrades in the future by only pulling 7 wires? The run looks to be maybe 25 feet, all in the attic.