Yes, a woman's first labor is usually her longest, with each succeeding labor likely to be shorter. This is because your cervix, vaginal passage, and pelvic floor muscles have never been stretched or dilated prior to your first birth. The uterine contractions that occur during labor accomplish this stretching to allow the baby to move out of the uterus and into the world.
The average length of a first labor is 12 to 24 hours, with the greatest part of that time being early labor. This time is usually divided as follows:
Your second and succeeding labors are usually about half of this time, although every labor is unique and the length can be influenced by many factors. The best plan as you approach your labor experience is to have NO plan! Labor will flow in its own best time, so relax and allow it to happen.