Sustaining revenue growth is difficult because most product markets have a natural life cycle. First, a product must prove itself with early adopters. If it proves itself, revenue growth takes place as more buyers want to buy the product. Naturally, the product reaches a point of maximum penetration. At this point, growth slows, or even declines. The way to find new sources of product-driven revenue growth is to launch new products to new buyers at the right time to enjoy a long-life cycle.