Northcote Parkinson, writing in 1955, semi humorously proposed his ‘law’ that “Work expands to fill the time available for its completion”.
This is very true. Staff will often take as much time as is available to them to work on a project even though that might mean unnecessary embellishments.
Even good staff do this because they want to seem to be busy and not slacking off.
You have to learn how to judge been useful work and time-filling work.