Learning to estimate how long projects take is a useful skill. It's difficult, too. But it can help a lot (and there is also an associated skill of finishing a task in the amount of time provided).
I was talking with my friend Eve, who had been asked to edit something for a friend/acquaintance. The proposed budget: $200; the project: 400 pages. The friend was asking Eve to edit each page for $0.50. Which may seem generous; I agree that $200 is a lot of money. Except how fast do you read? Let's say, just for the sake of argument, that you can read a page of text in a minute. That's sixty pages an hour, or $30/hr. Which isn't a bad little wage. I don't read 60pages/hr. At my fastest--easy reads--I read maybe 50 pages an hour. That's just reading. When I'm editing I go slower still: it's necessary to read closely, and to figure out how to fix sentences whose meaning is unclear, and to fix any minor errors. At my fastest, when proofreading a well-written document with few errors, I might edit about 12 pages an hour. Proofreading is painstaking work--in the sense that one should take pains to get it right: the point of proofreading is to eliminate errors; it cannot, therefore, be done in a lackadaisical manner. Twelve pages an hour--that's $6/hr at $0.50 per page. Now Eve may be willing to take the project as a labor of love, but that's not a very generous offer to your friend to offer them $6/hr for a project that takes skill, care, and would take over 30 hours of work. I'm not suggesting that the friend is uncaring, but just that they weren't making a very good estimate of what the project would take.
Another example. I had a sobering exchange with a writer recently. He approached me with a week before his deadline, and there simply wasn't enough that I could do in a short time. The biggest issue was a concern with some of the content. With only a week there was no time for any give and take between the two of us. Especially (even if one were to assume that I worked instantaneously) if I had any questions that he needed to answer. There were--both matters of content and idea, and of execution--for example, there were many reference citations in the text that were not made in the reference list. He had estimated that a week would be enough for an editor to work; I can do a lot in a week, but he had not made any estimate for any work that he might have to do in response to what I saw (like the need to fix missing citations).
A related issue is that of getting feedback from professors--a notoriously difficult task. If we have a big draft and if we want detailed feedback, we have to realize the effort that we are asking from our professors. A short dissertation might be 100 pages. To read it closely might take four hours. To write comments and feedback could take another hour. That is not a request to make lightly of your committee, even if they do owe it to you to give you good, clear feedback on your work. It is important to correctly assess what you are asking of them in order to have reasonable expectations of what you can get back. And what if your draft is 200 pages? Or, like my final drafts, over 300? I respect tremendously the work of my dissertation committee--Professors Jean-Pierre Protzen, Eve Sweetser and Greig Crysler--who all read three drafts, and commented copiously during the last six months I was writing. I appreciated and marveled at it then, but now, having worked as an editor, I respect the effort even more. If they were working twice as fast as I do, they were spending six to ten hours on each draft. Adding in the other help they gave me in the final semester, I would estimate now that each gave me almost 40 hours of time in the course of twenty weeks.
It's important to estimate the effort that goes into tasks, not only to help us manage how we work with others, but also to help us manage our own work. If we have unreasonable expectations of ourselves, that can be as harmful as having unrealistic expectations of others. Writing is a difficult process, and one during which you learn a lot about what you're trying to write about. Usually you learn so much that at the end you'll look askance at what you wrote in the beginning. That's not a problem--that's an opportunity to grow. But if you haven't given yourself time for that, then you're going to get into trouble.
I had an inquiry once from a writer: "I can only work with an immediate deadline; I have to write my entire dissertation in six months." Is that a realistic estimate? Can that plan of action work? It seems to me that estimating that you can finish the whole dissertation in six months, when you can only write on immediate deadlines is a naive plan. Wouldn't it be better to estimate accurately: "If I don't change how I work, so that I can work regularly without an immediate deadline, I won't be able to finish in the six months I hope?"
Good estimating plays a key role in making good plans. Whether estimating the needs you will face, or estimating the help that you can get from others, if you can realistically assess what needs to be done and how long it will take to do it, you will be far more likely to get your project done and far less likely to suffer the emotional strain of unpleasant surprises and frantic attempts to make the final deadline.