Even when I have a quick call on my calendar, I always try to block off an hour.
That does a few things:
First - if the person is late to the call (I try never to be late ... more on that below) ... then you can still talk to the person and not reschedule.
Second -- You'll never have more than 10 meetings scheduled in a day. Which is important for your sanity.
Third -- you will also have lots of opportunities to carry out your microtasks (like keeping up on email) throughout the day - because if your meeting only lasts 20 minutes (which is the avg length of my phone meetings), you'll have another 40 minutes for tasks, meeting follow-ups, etc.
Fourth - you won't be late for meetings and you'll be able to respect other's time as you would want them to respect yours.
