More support for incorporating early is that the date of incorporation is important to some organizations and if you aren't incorporated, they'll simply pass on you.
Having been incorporated for the 5 years prior has value. Of course it depends on what you are selling.
additionally, it protects your personal assets, like your home, if you get sued.
Additional support for incorporating (at least with simple Delaware based LLC) early; if you build something and can pick up a partner they are far more likely to 'take' any IP generated as a result of products built during the partnership if you are a single, lone wolf contractor. If you get an EIN (employer identification number) and put that on your W9s you can negotiate from a company position for shared IP (as we have - 2 patent applications and the legal work is being paid by our partner...we'd never have been able to close that as two people working together to build a large corporation something).
Having been incorporated for the 5 years prior has value. Of course it depends on what you are selling.
additionally, it protects your personal assets, like your home, if you get sued.