Silt and Sun
Unless otherwise specified you can assume that you can take as many short rests as you need to have the leader use her encounter healing powers to heal you to full. This means that when you spend a healing surge during a short rest, you can an additional bonus equal to the average bonus given by the leader. Right now the bonus is +3.
For the most part, you cannot gain the benefit of an extended rest without gaining two milestones first. There might be some times where I explicitly say this rule doesn’t apply, and you may have to have more encounters than just the two milestones, but it is a good rule of thumb.
I will try to plan the encounters so that you should be at a good plot point to rest after you get at least two milestones and not before.