You don't need 10 years, you need 10,000 hours. However, 10,000 hours alone is still a useless metric unless you know it was spent learning. 10,000 hours fixing

You don't need 10 years, you need 10,000 hours. However, 10,000 hours alone is still a useless metric unless you know it was spent learning. 10,000 hours fixing bugs in the same system won't introduce you to enough new concepts to provide the same value of 10,000 hours of building products.