There is a lot of sound information in this thread. However, I have a different take on it. Here goes...
First - I recommend not rushing at a hellacious pace just to cover the entire
Camino Frances. You will miss much of what the Camino has to offer. It is simply not worth it IMHO. Even if you have to split it into two separate Caminos to get it done, you will in the end, appreciate doing it all. Trust us all on this observation. I suggest that the Camino is about quality, not quantity (as in how fast you can cover the distance).
Splitting it into sections is something many Europeans can do as travel to and from is relatively easier. However, if you are coming from farther afield, like North America, Australia / New Zealand, or Asia, you need to plan to do it in "one-go," as logistical concerns are usually more pressing.
Also, not having enough time to do it sort of identifies you as being either from the US or Canada. Most everyone else around the world has far more generous holiday time. I am retired and have the means to make several annual trips. So as long as the family is supportive, I am outta here..!
In 2013, (first time) I had medical problems that caused me to make a command decision to skip several days walking, to seek medical attention (minor foot surgery on both feet by a podiatrist at Burgos) then some days to walk more lightly and recover. I had to taxi over several days into Burgos to seek medical attention for my feet. After the surgery, I was told to "stay off my feet - no Camino manana - para dos dias... So, I was in Burgos for three days.
On the recovery days, I would start out walking, then stop at a cafe after a few hours depending on how my feet felt, and have the proprietor call a taxi to cover the remaining 8 - 12 Km. Plan on one euro per kilometer on average. Do not tip, but do round up. You can cover a lot of ground more quickly using this "Morse Code" approach.
I also used buses to travel from town to town. There are apps for your smart phone for ALSA and the other major inter-city bus lines. You may have to switch to the Spanish iTunes App Store to locate the apps. But once you load them at home, updates flow without problems. Many of these apps have English capability.
I felt bad about having to skip anything, especially my first time, but needs must. I made a promise to myself to return ASAP to walk the bits I missed.
In 2014, I returned and did walk the bits I had to skip over the year before. However, rotten weather in some places and my knowledge of which spots were muddy, sloppy, and not amusing, caused me to skip other stretches I had walked in 2013. However, I always make sure to be able to walk the final stretch from Sarria to Santiago.
So, it did take me two years to cover every step of the entire
Camino Frances on foot. In the process, I walked at least 2/3 of it twice. But to me those were the "high points."
Second - if you are using the
Brierley Guide, as at least a third of all pilgrims do, have a close look at how he treats major towns and cities with surrounding industrial parks or estates. Typically, cities like Burgos and Leon have outer "rings" containing light and medium industry, trucking firms, warehouses, and generally soulless walking conditions. it can take from a half, to one-full day to walk through these areas.
Also, some pilgrims hop on a local bus as they emerge from the more pastoral countryside, riding a bus either into the city center, or sometimes to skip the major city altogether. Leon is famous for this. Just find a bus shelter on the major surface road you are on. A bus will come by eventually. If you are lucky, you can find a web site for the local transportation authority. You can also ride a bus heading out of a city to avoid the industrial areas on the west side of the city.
Third - with the exception of the final 100 Km or so (111Km actually) from Sarria into Santiago, there is no sacrosanct requirement that you actually walk every last kilometer. Put into an historical context, if you were a medieval pilgrim a thousand years ago, and a farmer offered you a lift on his wagon or cart into the next village, town or city, would you be wrong to accept? No, you would not. Hence, riding a bus or taxi to skip one-half to a full-day's walking entering or leaving a major city is not inappropriate. It is YOUR CAMINO. No one else can judge the "correctness" of your effort. That is a very private and individual matter.
Overall - If you review the guide you are using (I presume
Brierley but it could be another), and plan your daily stages closely, paying attention to his noted alternatives for skipping over the less scenic or more soul-sapping parts, you could easily follow the rest of the more-or-less standard stages and still finish in less than a month.
To do the entire thing, "according to
Brierley," as written, takes 33 days, plus time to get to your starting point and time to leave Santiago. Some say that number was intended to emulate the number of years Christ lived on earth. Others maintain it is coincidental. Whatever... I tell people the time needed is a month, mas o menas...
The fact is that, if you manage your daily walking using taxis or local buses to skip the unappealing (to your assessment) bits, you can easily pick up four or five days from that 33-day number. Do not forget, if possible to allow one extra night at Burgos and Leon, and Santiago before pressing on. There is so much to see at these cities, and other places that it beggars belief that some would skip over through or around them. Personally, I try to spend two night at Burgos, Leon, Astorga, and on arrival at Santiago whenever I can. I love Astorga personally. It is also the capital of the Spanish chocolate industry. Ah HA! Bet you did not know that Spain is known for its chocolate too?
Be sure to allow the time at the end to avoid rushing to get through the Pilgrim Office welcoming process and rush out of town on a bus, train, or plane. I recommend savoring your arrival at Santiago. It can be deeply spiritual and emotionally satisfying. Your emotions are typically in a tizzy anyway, after a month on the Way. many of us suffer from a malady called "Santiago Syndrome." You will understand when you get there.
IMHO too many people plan too tightly, and have to get through the Pilgrim Office process to make a flight or bus that evening or early the very next morning. This is regrettable to my way of thought. I like to recommend that people spend at least two nights there. Most albergues will allow you to stay the extra night. Besides, there are a lot of alternative housing options for inexpensive stays. The only time bed space gets REALLY tight at Santiago de Compostela is around Santiago's Feast Day on 25 July. Last July, there was like literally no room at the inn for arriving pilgrims who had not booked ahead.
I hope this helps.