There's also a certain amount of positive feedback, I suspect - once you've had one hit, people will want you to write for them and, because it probably sounds

There's also a certain amount of positive feedback, I suspect - once you've had one hit, people will want you to write for them and, because it probably sounds hit-like (which stands to reason since your style has already been a hit), it'll stand a good chance of also being a hit which means more people will want you to write for them and rinse, repeat, cash cheques for 20 years, etc.