How can I show the remaining time for a caffeinate command?
pmset -g assertions will show the caffeinate-generated assertion (among others) along with how many seconds remain:

   pid 23694(caffeinate): [0x0013076c0005a0ed] 00:37:55 PreventUserIdleDisplaySleep named: "caffeinate command-line tool" 
    Details: caffeinate asserting for 7200 secs
    Localized=THE CAFFEINATE TOOL IS PREVENTING SLEEP.
    Timeout will fire in 4924 secs Action=TimeoutActionRelease