How long does it take to get a No.1 hit? In the case of the ‘70s group Ace, fronted by singer Paul Carrack, the answer is 45 years. The British band’s 1975 single “How Long” originally reached No.3 when it was released, but this week it made it to No.1 on Billboard's Rock Digital Song Sales chart, selling 4,000 downloads, reaching 831,000 streams and increasing sales by more than 2000 percent. The reason behind the song's sudden return to popularity is its use in a new ad for Amazon Prime titled “Binge Cheat,” which features the song’s opening line, “How...