Very much so. I'm currently in the process of writing a trilogy of trilogies, for which there's a loose outline of each book and the major plot points. However,

Very much so. I'm currently in the process of writing a trilogy of trilogies, for which there's a loose outline of each book and the major plot points. However, the detail of exactly what happens is left up to me as I find it in the moment. It's something several acquaintances of mine who are published, successful writers subscribe to. One recently summed it up nicely as "plan the mountains, write the valleys". The major advantages are that it gives you the ability to write the ending first, so you don't get to the end and discover that you need to dig yourself out of a hole, and that you can keep things internally consistent, ensuring people don't magically teleport around the world (unless of course that's actually a thing your characters can do). There's something to be said for not over-planning, but also for giving yourself enough time and room to be able to spot problems ahead of time so you don't write yourself into a corner.