In 1991, Cat 3 would have been standard cabling for both telephone and 10BASE-T ethernet. The advice to pull extra cable is definitely spot-on. The labor to install the cable is such a large component that it makes sense to spend a small fraction more to get expandability and redundancy. I absolutely dread climbing into an oven-like attic with fiberglass insulation to run another cable.
i7-4770K, H70, Gryphon Z87, 16 GiB, 980Ti, SSD, 2 HD, Blu-ray, SB ZX, TJ08-E, SS-660XP², 3007WFP+2001FP, RK-9000BR, MX518