Post History
I totally agree with the answer given by Tommy Myron, but I think there is one thing to add about the way you look at this question. I think whether you decide to use your ideas now depends on whet...
Answer
#3: Attribution notice added
Source: https://writers.stackexchange.com/a/17184 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
I totally agree with the answer given by Tommy Myron, but I think there is one thing to add about the way you look at this question. I think whether you decide to use your _ideas_ now depends on whether the ideas concerned are or are not naturally **part of your current _plot._** If they are, i.e. if they fit harmoniously into the series of events that you consider will wrap up quite nicely at the end of Book 2, then put them in. Don't worry that you will use up all your good ideas - your supply of good ideas is not a fixed quantity, your subconscious will send you more as you need them. However, if the good ideas you mention are "worldbuilding" ideas, or are ideas about side-plots or side-characters to your current story, then however excellent they are in themselves, putting them in would just bloat your current story. Make just enough mention of them to ensure consistency with your future books if ever you write them, and leave it at that. It's true that you may end up never writing any future books in that world and never using those ideas. But fear of future waste isn't a good reason to make your present work less good than it can be. Putting it bluntly, all of us could be wiped out by a mutant star goat eating the planet tomorrow. Or less dramatically, any one of us could die by some prosaic cause, or suffer some non fatal but life-changing event that stops us writing before we ever finish whatever we are working on. Then all our good ideas would be wasted. I say "we" because I am currently struggling with exactly the same issue of a fictional universe whose growth has outstripped my original story idea as you are. (A general question: Would it be possible, and would it be considered good etiquette, to duplicate this post in the Worldbuilding stack exchange?)