...
Completing tasks sooner is recommended because you will build your time reserve. For instance, finishing 14 days long deadline in 4 days will increase your time reserve by 10 days (14 - 4 = 10 days), so you will have more time for your next deadline. If your next deadline is 14 days long, then you will have 24 days to complete it. Completing a sprint early provides a time buffer but does not change the deadlines of upcoming sprints.
...
We recommend always focusing on completing sprints sooner than the defined deadline, as being close to the deadline puts you at a high risk of missing it. This will help you to build up a time reserve and reduce stress while working on sprints.
...