Not just the domain knowledge, the access you have to your target market. 15 years is a long time to get to know people. Customer development will be a breeze,

Not just the domain knowledge, the access you have to your target market. 15 years is a long time to get to know people. Customer development will be a breeze, you could literally shoot the shit with your peers, and take notes afterward. You'll also have a head start when you start marketing too, because you can start by telling everyone you know in the industry.