If you have an opportunity that would make it worth it, I'd say go for it. If you're doing it for your own satisfaction and sense of accomplishment, go for it. If you're just generally doing it, and don't have a specific need or drive for it, I would not go through the trouble. If you were a Civil Engineer, it can certainly be worthwhile to have your PE, but as an ME, there aren't a lot of things that require a PE, so in my opinion having it doesn't add much value. I'm a non-PE ME, and while I regret not taking the FE back when I was fresh out of school and remembered a lot of stuff, there's no way I'd do it now with a brain that is full of the fog of life.