There are still myths about CIs, most of them untrue. I've heard that the longer you haven't heard out of that ear, the less likely it is that a CI will work. Hah...a friend who had lost all hearing by flying through a windshield when he was less than 6 mos. old got a CI when he was in his early 60s...and found it useful almost as soon as it was turned on. There's also a myth that the older you are, the less likely it is to work. Hah, again! A friend in her late 80s hadn't heard well for years, then had a stroke, which further impaired her hearing--but, when the CI was first turned on, she could understand and hear things again. Her husband complained that he couldn't play poker at his house any more, because she now knew how much he was losing! She also had never allowed him to use swear words, but he'd used them liberally during the years she couldn't hear much, so that was another thing he had to change. Actually, he was really proud of her new ability to hear and quickly made the necessary changes.
It IS true, however, that you need to be willing to work to learn to get the most out of the CI, from what I've heard. Even the people who can hear some things almost immediately, need to work on learning to improve their hearing. It's pretty much the same as people who get bifocals in their middle years after never having needed glasses: they need to learn to use them, unlike those of us who've worn glasses most of our lives. When I got my first pair of multi-focal glasses, I was thrilled to learn that trees have leaves, buildings have doors and windows, those big green things on the freeway are actually signs...who would have guessed? I had no trouble adjusting whatsoever, because the gain was so great. Same is true with hearing: the more you gain with an aid or aids or a CI, the more you'll be willing to work to maximize the gain.