Coming from traditional project management,
time-based estimates (man-hours, man-days etc) are still used quite often and in most cases prevent the teams from unleashing their full Agile potential
Why is it a problem?Time based estimates require you to have all the work pre-assigned (which often causes silos) and
take a lot of time while causing more problems than they deliver value. How do you evaluate uncertainty? Add 3 extra days to the estimate and pray for the best? How would you estimate a piece of work that requires someone to work for 1 hour per day for 15 days - is it 15 hours or 15 days? If you put 15 hours, you risk ending up with a wrong timeline, but if you put 15 days you will be overestimating resources needed.
What can you do?Identify whether you need any kind of work estimation at all to begin with. Quite often you don’t - if your backlog items are more or less similar in size, just estimate your velocity with number of items team completes per week, then make future projections using this information. Otherwise explore
t-shirt sizes and story points estimation; time-based estimation should be your last resort.