My horse is nine and schooling 2nd/showing 1st. He's a talented boy, but spent the last couple of years in a field and raced until he was 5. He's also shown Novice eventing and will do so again this year - I'd love to somehow qualify for the Novice long-format at GMHA. :)
As someone said, dressage is really all relative. It's about progress, so as long as you and your horse are making (correct) progress and having fun, that's all that matters!