I always have such high hopes for my future reading plans. My to-read shelf on Goodreads is 486 items long, and hasn't shrunk since I joined the site. I just keep adding to it, and I always forget to add the books I actually own.
If I keep a book once I've read it, it's either because I want my husband to read it, or because I want to reread it. Rereading is part of my high hopes for reading, but then I look at that list of 486, and I renew my hope to make a dent in it, and I toss rereading by the wayside.
That's changed a bit this year. So far, I've reread the first three Toby Daye books by Seanan McGuire (reviews for books 1, 2, and 3), and my participation in Austen in August means I'm rereading Sense and Sensibility and Mansfield Park, neither of which I remember reading the first time around.
There are good reasons for rereading, beyond simply that it's fun. Repeat readings allow you to read in more depth, to look for foreshadowing, to better analyze the text. When you reread a book, you're not just absorbing the story, anymore. You know what happens next. You're seeing how it was done, and you can pay a lot more attention to the craft while you read.
That doesn't mean that you should only reread books that are perfectly crafted. I would advise, at least if you're trying to read as a writer, that you read books that do something you want to learn. If you greatly admire one writer's dialogue, and that's what you want to know more about, read and reread that writer's books. If another does worldbuilding in a way you admire, that's who you want to read in depth. Any book that's made you say to yourself, "I'll never be this good" is a tool at your disposal.
There is a line between emulation and learning from those who have come before, though, and I would caution you not to cross it. Your voice should still be yours, and you should still use your own style and unique way of looking at the world. Use other writers' tools, but not their products.
Like most things in my life, which books I choose to reread or read for the first time are a matter of which I feel like. I don't make lists, I don't schedule books (unless someone's asked me to review one or I take it out from the library, which bumps it up in the queue), and I certainly don't plan when I'm reading what. My reading priorities, too, are by the seat of my pants.
But, I'm glad I was able to learn the value of rereading, all on my own. It's one of the things that's helped me learn to be a better writer. Anything that helps with that is well worth the time.