1500 hours is a huge number. When you're looking up at it. When you're looking back at it, it is a much smaller obstacle.

One learns when one reaches his limits of experience. Once you get to an airline, you tend to not push those limits(and your passengers thank you for that) and so learning slows. Thus, you get more out of 1000 hours as a CFI than you will in 1000 hours of RJ flying.