Playing a warrior, I almost always had unused skill points, even near the beginning of the game. I'd save them up if there were a couple skills I wanted to get when I got to a certain character level, and didn't put points into skills unless I needed them (later in the game I could be freer with skill points). At the end of the game I had 10 unused skill points, after putting 5 in a skill I did not use and topping off a few I didn't need once I got to the wastelands.
Mage spell books can be bought, so that can help alleviate a shortage of skill points.
