I walked in March and it was not crowded (I'm guessing it will be similar in October). I met several people who stayed more than one night in an albergue--not due to injury but just for a rest day. I guess it would depend on the hospitileros. With the people I met, hospitileros let them stay an extra day if it wasn't crowded. When I arrived in Santiago, we stayed 3 nights at the Acuario Albergue without any problem.
I would suggest you take at least 1 book. I took 5 from Granada to Santiago and left them at albergues/hostals as I finishd them. It can be surprising how much time you have free after walking-one comment on this forum said that they were so desperate for reading material they were reading their clothing labels! I also got gastro from le puy last year and spent 3 loooooonnnngggg days in an out of the way place with only french magazines to read.
My understanding is that Municipal Albergues will only allow pilgrims to stay for one night, unless sick or injured. Private Albergues do allow pilgrims to stay a 2nd night, and I did this when staying at the private albergue in Astorga.
Agree with Omar about books. As I walked only around 20kms each day, the long afternoons sometimes dragged without something to occupy my mind. The 2 books I packed were soon read, and I left them in the albergues for others to pick up. Many albergues have a pile of discarded pilgrim gear, including books, so it's great to find English reading material. I found a 4 week old, well-read, English newspaper in one and spent hours on my bunk reading it from cover to cover. A Dutch pilgrim suggested getting Sudoku puzzle books, which are great as language is not a problem with these, and the books are available all over Spain.
I suppose it depends on the hospitalero. If the albergue is absolutely NO crowded, and the pilgrim has any important reason to stay a second night.
For example, if you enjoy very much the kind of art which is the local museum, and for you is VERY important to visit it and spend several hours to do that, or ... I don't know, but it depends on the hospitalero. The rule exist only for general reasons