do you mean at 'work'?
it depends
for simple tasks, i'll do them as soon as i am 'authorized' to do the work, so a deadline would be meaningless, it'll be done before the boss can shoot me an email or laminate a timeline, etc etc
if it is more complicated where i need time to think of how the work will be done, then i need a timeline/deadline so that i don't wait too long to begin the actual work