Many different factors impact the speed of labor. They include the baby's position, the strength of your contractions, and many other things that are harder to put your finger on. Some women's labors slow down if they are afraid, for instance. Some laboring moms notice their contractions slow down if they labor in water (see what is a water birth?), while an epidural can do the same thing. On the other hand, epidural anesthesia can also sometimes speed labor up. In addition to these and other factors, whether you are a first time mom or have already given birth before also impacts the speed of your labor.
Statistically speaking, second labors are indeed faster than first labors, but not by as much as many women would be hoping. Women giving birth for the first time progress 1.2 centimeters per hour on average, while experienced mothers average 1.5 centimeters per hour. Pushing also tends to take less time for subsequent labors. This does not mean that you should expect an easier labor, although second labors can indeed be much easier (perhaps also because you know what to expect the second time?). It does mean that you might want to head for the hospital or birth center a bit more quickly, or call your midwife earlier if you are having a homebirth.