Here's another idea: for every chart you make, make a more abstracted chart that will provide new entries once those in the first have been used up.
The good thing about a more abstracted "spur" type chart is that it can generate scores more results and how you interpret those results can very from day to day (and whether you get help from your players) meaning even more possible results. The bad thing is that it requires that you interpret those results. And that requires some confidence, mental clarity, and maybe time and some of them may just end up being duds.
The good thing about the specific chart is that you can put what you know are the most badass, fun, and appropriate to the unique qualities of that topic. The Bad thing is you may not be able to think of all the most badass possibilities. Or, you may just use them up in play. And then what?
Make both. Now, that means more work, but you want the best "What the Gnome Bard Has in his Pockets" chart possible right?
(Extra credit: Zak lays out some chart taxonomy here)