\"How Long\" is a song by the British group Ace featuring Paul Carrack. It was released in March 1975 from the band's 1974 album Five-A-Side.
It reached #3 on the US and Canadian charts, #1 on the US Cash Box Top 100, and #20 on the UK Singles Chart.
Although widely interpreted as being about adultery, the song was in fact composed by lead singer Paul Carrack upon discovering that bassist Terry Comer had been secretly working with the Sutherland Brothers and Quiver. Comer returned to Ace in time to play on the song.