Jackson is almost 6 and still humps Pillow Pets. LOL... luckily no real people or animals though, just the stuffed variety.
My dads female JRT was spayed at 5 months or so, and she is now 7ish... still humps a stuffed duck. AND my dads Dachshund mix also fixed was just caught humping the REAL cat the other night
Good luck...
haha... honestly? It's more of a training issue. We just don't really care or bother to stop them as it's never been a big problem.