There are two types of schedule, which I'll call the manager's schedule and the maker's schedule. The manager's schedule is for bosses. It's embodied in the traditional appointment book, with each day cut into one hour intervals. You can block off several hours for a single task if you need to, but by default you change what you're doing every hour.
Like almost all of Paul's post, this one goes on brilliantly and it's a must read for anyone who works regularly with developers.
A great prequel to Paul's post is a 37 Signals post which is now 3 years old, which I refer to often: There's No Such Thing as a One Hour Meeting.
It’s no mystery that we’re meeting averse, but here’s another reason why we think meetings are toxic: There’s no such thing as the one-hour meeting.
If you’re going to schedule a meeting that lasts one hour and invite 10 people to attend then it’s a ten-hour meeting, not a one-hour meeting. You are trading 10 hours of productivity for one hour of meeting time. And it’s probably more like 15 hours since there are mental switching costs associated with stopping what you’re doing, going somewhere else to do something else, and then resuming what you were doing before.
The key takeaway is that there are opportunity costs associated with everything, and the opportunity costs associated with meetings are frequently underestimated, often to a significant degree.