To listen closely; pay strict attention Often a brusque command: He can make you listen up with that violin of his(1960s+ Armed forces fr black)
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with long haul
A considerable distance over which something must travel or be carried. For example, It's a long haul from my house to yours. This usage dates from the late 1800s, as does the antonym, short haul, as in The movers charge just as much for a short haul as for a long one.
A considerable length of time, an extended period, as in This investment is one for the long haul. It is often put as
over the long haul, as in Over the long haul we needn't worry about production.
[ c. 1930