Possible Fifth Book?

On the way to Southampton I had an idea for a fifth book, the main problems are the fact that I cannot write it yet and I do not know if I have the skill required to write it as I imagine it. More on this over the next few years as I think about it. When I think about the works from the authors that I read, they all had recurring characters in new stories and that his been true for the books I’ve read for the last half century. Even Stephen King wove characters from one book into another, which stretched your mind, but did not matter if you had not read any other. I look at my proposed stories and nothing overlaps, no trilogies, sequels, prequels and each is “stand alone” and I wonder if this is a good thing. At nearly sixty I will only get one shot at this.