It absolutely depends on what your objective is. Submaximal strides are more about adjusting muscle tension and maintaining neuromuscular efficiency at higher speeds.
For a miler, for example, the vast majority of your mileage is at a pace much, much slower than race pace, so it's good to get more practice at moving your body in the way it'll move during a race. There's nothing wrong with throwing those pickups into a longer run when the weather is cold.
If your primary objective is to increase muscle tension, then it's better to do them after the run.
If your primary objective is increasing top speed (which correlates with long distance performance and contrary to an earlier suggestion IS an important objective for endurance athletes), then it doesn't matter if they're pre or post run, but they shouldn't be intra. You should be warmed up, you should gradually accelerate to top speed, and then you should take several minutes between reps. This is akin to weightlifting. You can also do these on a hill, which seems to reduce the risk of injury and also makes it possible to recruit even more muscle fibers (think of how cyclists are capable of producing their highest wattage numbers while climbing).