That could be entirely normal. Things that can extend the cleaning cycle are temperature boost (if the incoming water isn't hot enough), and the cycle chosen, and whether you choose a drying cycle. Many also have sensors that look at the water going through the pump to see how dirty it is, and extend the cycle if that looks dirty. A pots and pans cycle is often longer than a light, or china setting.
If the dishes are clean when it's done, my guess is it is enitirely normal.