If someone lives to 200, 500, 1000, does their brain "fill up", run out of room for new memories? Do you forget entire decades from earlier, do you stop being a

If someone lives to 200, 500, 1000, does their brain "fill up", run out of room for new memories? Do you forget entire decades from earlier, do you stop being able to form new long-term memories? Do you pick up a book and wonder if you've read it before? How many times?