Although Long's paintings commanded high prices during his career--one of his pictures sold for the unheard of amount of 7,000 guineas in 1875--his reputation has since faded and his work is not much in demand. A large collection is in a minor museum, the Russell-Cotes Museum in Bournemouth, England.

His specialty was large paintings with subjects taken from the Bible and from history. He was also a successful portrait painter. He exhibited his work at the Royal Academy from 1855 until the year of his death, 1891, and he was a member of the Royal Academy (1881).