Actually, I think it's the inverse. Most 2/year novelists are professionals, and it shows. Stephen King consistently wrote at about that rate. 6 months
full-time is a good amount of time for a professional writer: 1-2 months for writing, and then another year or so of polishing and editing that happens in parallel with other efforts.
10 year novelists are often amateurs. That novel your next door neighbour asked you to read? He's probably been working on it for years.
Even notoriously slow George R. R. Martin takes less than 10 years to write a novel.
