I think the main thing you would miss is the connection with the people you meet along the way. To me it was more important that I walk every step of the way than that I get to the end, now. That would have been my ideal but I only made it to Fromista my first year when I both ran out of time and was done in by the burning in the soles of my feet. I had family commitments the next summer so no walking, got sick on the Camino (but my most treasured Camino memories) and only walked 75 km the next year, then finished the following summer. All in all, that is a four year commitment.
Some people only make a one year commitment. Over and done -- in x window of time. I did it the way that was right for me. Just starting, 2005, when no one I knew had even heard of the Camino, was a new vision of myself. Coming back and joining the Camino wherever I left off was like meeting up with an old friend.
It's your Camino. Do it your way. I have the impression that most Spaniards do it in sections.