Many startups end with the sale of the company.  Sometimes this is "early" in development, sometimes it is later.  I learned a sad lesson about patents when we sold DoBox.  Although you are the inventor listed on a patent, once you've assigned the rights to your company (and then sold that company), you no longer control that patent.  In fact, once you've sold the company and the patent, under certain circumstances you're not even allowed to get information about it! However, it's still in your professional best interest for that patent (or patents) to be prosecuted.

If you sell your company, here are some suggestions

1) Get the acquiring company's agreement in the contract that they will use all reasonable efforts to prosecute the patent(s) and protect the IP developed under your leadership
2) Put in writing that they will keep you appraised of the status of the patent prosecution at least every 6 months (and if they don't, that you have the right to go directly to Counsel to obtain such status info).

While we're at it - put in the acquisition contract that the acquiring company will either a) agree to keep and protect your domain name for 20 years (a whopping $160 investment) OR that they will transfer it to you at no charge if they decide the do not want to keep it.  Make sure that they agree to any costs to REACQUIRE it, if they screw this up! You don't know what might get put on a domain that was closely associated with your name and reputation if it is picked up my one of the domainers.