I don’t assign deadlines to my staff. They know their schedules better than I do.
I assign the amount of time to spend.
This isn’t because I know how long it will take. It’s because I know how big of a problem they are solving. I know the difference between a 15 minute problem and a 5 hour problem. I make it clear to my staff how long they should invest in solving a problem before coming back to me. That doesn’t mean that at 15 minutes they give up. They know that at 15 minutes they need to reevaluate their approach, or come talk to me to discuss challenges, roadblocks, decisions, or opportunities to learn.