Not sure in 9ball, but there's an element of randomness involved. I'm no pro but I once ran a seven-pack in about 2000. It included a nine on the break and three early combos on the nine. I recall giving up a five-pack to Mika Immonen in about 2004, but I don't recall anything more than that. In straight pool, I've had to sit and watch three runs of 200+ against me, two of them by Tony Robles and one by Mika Immonen.
As a live fan of tournament play, I was present for Appleton's world record of 200 at straight pool. At rotation pool, I've seen two different eight-packs. One of them was by Souquet at 9ball and the other by Dechaine at 10ball. Although many have offered that Lassiter once ran a 21-pack, the longest fully verified package I know of on a nine-footer was the fifteen-pack by Niels Feijen in 2003.
According to an AZB website article on 2/2/2003:
In a 'challenge match' against French player Donald Du Bois, Feijen broke and ran 15 consecutive 9-ball racks on a regulation 4 1/2 X 9' table.