It's true - the clock is always ticking with good candidates.
With bad or average candidates, you can really do what you want. Take your time, be indecisive, lose focus - whatever - bad to average candidates will be there whenever you get your act together and actually want to make a hire.
Good to great candidates are different. They've got a lot of reasons not to switch, or if they're an active candidate, they've got good to great options on the table. They don't have to wait, and in most circumstances, they'll be gone in 14-21 days. That sounds like a lot of time, but it's not... mainly because you have 3 to 4 points in your interview process where things usually stall out.
With bad candidates, you can stall at all of those points and have limited risk of losing them as candidates. That's why they're bad candidates, right?
Good to great candidates age faster than homemade bread with no preservatives/chemicals in it.
Stall at your own risk. Forward this post to a hiring manager if needed to emphasize the best candidates in the candidate pool will be gone by the time they get back to the hiring process. Or they won't trust you after that and simply stop returning your calls - mainly becuase the heavy courtship present early stalled out.
You've got 14 days from the time of the first call - max.