I think it is reasonable to assume that Prince Harry would be considering settling down into a permanent relationship sooner than later, because of his position in the Royal Family. I wouldn't think he would want to be single for a long time, even if he does just marry for convenience.
Let's be realistic here. Prince Harry isn't much different than the rest of us and at his age he's probably looking to start a family or at least have a steady significant other. I think it's silly to question his intentions because he's the one that has to live with it, not the world.
I think he always had a set age in his mind of when he would like to be settled by. I think it was later than Prince Williams, but still probably before he's 35. He has said that he would like a family so I do not think he will wait too much longer.
I do not believe that Prince Harry is ready to settle down. His single man antics have been widely documented for years and there has never been any hint of him slowing down. Perhaps in the distant future he may find a bride to suit his needs, however I believe that he's not currently interested in starting his own family.