least 3 – 4 weeks before the relay. for example, once you know what your legs will be (especially your longest leg) schedule two runs within an 8 – 12 hour period in which neither run is as long as your longest leg. again, there are plenty of people who do just fine without running any doubles. if you have a good, solid base of miles, you will probably be just fine. however, if you want to know what it will really feel like, consider running a few doubles.
when it comes to pace, you should be able to hold your 10k race pace for your first two legs quite easily 