My thoughts is that it is really up to you. I've done the whole thing 2 times and walk again in 2 weeks . My wife and a friend did the Valcarlos route the first time, then she went with me over the top the second. We are in our 60's. She found both hard, and was very tired after doing the Napoleon. As has been said here before, it depends on several factors. First, what shape are you in and how hard have you trained. I've seen people who have said they trained hard but found they only did short, flat mileage every day with no hills, they found it very hard, if not impossible to do Roncesvalles; others that said they did little training but were in great shape (not overweight) did it fine. The second is when you plan to do it. I admire people who get off the train and start walking, but Orisson or Hunto should be their goal for the day. To do Roncesvalles takes a whole day, starting at about 7 am. Lastly is the weather. It can be a hard slog if you can't admire the views of the Napoleon Route due to fog or rain. 2 days a that point or the Valcarlos route may be better, but as someone said, Valcarlos is not that much easier. Personally, if the weather is fine, I rank the Napoleon route as the most scenic and confidence building part of the whole Camino. If you think you are in shape and are aware of the distances and vertical you will be doing, and if the weather is fine, you will not regret it. Most people do it at their own speed, which is a key. The thrill of that first days adrenalin rush and the encouragement of your fellow walkers can take you well past where you where you normally would question your decision. Remember, the next couple of days to Zubiri, then Pamploma are relatively short and easy, as a rest.
However, I am not advising against stopping at Orisson if you do not have the ability or the confidence to continue on. I recognize that stop also can be a very worthwhile experience. If you can't go much past Orisson, there are other suggestions on this other parts of this website about a shuttle service you can arrange to pick you up where you feel like stopping, take you back to SJPDP and bring you back to exact spot you stopped, the next day. This is an alternative to stopping at Orisson and allows you to make it much further up the hill. It also relieves you of worrying about no beds at Orisson.
It is your Camino to do as you find fit for your ability and enjoyment. There are no rules.
Buen Camino