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.