What happens if i get interrupted by other work? It takes longer, of course. Anyway, i will give a different number is the question is “when can you complete this by?” than i will if the question is “how long will this take you?” The first is about when something can be done, and the second is about how much can i do.
My work isn’t billable. I understand why most people who do work that will be billed to a client need to keep track of their hours on a fairly granular level. (Although t don’t all.) There’s are reasons i don’t work for a consulting company, and the importance of timesheets is among those reasons.