short-timer

[shawrt-tahy-mer]

noun Informal.

a person, as a soldier, who has a short period of time left to serve on a tour of duty.

Origin of short-timer

short time + -er¹

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Even if Gingrich is a short-timer in the 2012 race, Romney should not despair.
2012 Flip-Flopping Olympics
Jill Lawrence
May 20, 2011

He was a pallid-faced, little dope-fiend of a short-timer who would do anything to obtain the drug.
The Jacket (The Star-Rover)
Jack London

"one whose term or enlistment is about to expire," 1906, from short (adj.) + time (n.) + agent noun ending -er (1).