If the ship travels tens of billions of light years will it eventually be traveling away from it's starting point at greater than c due to the dark-energy expansion of space itself? Or will the ship just red-shift more and more but never disappear from an observer with a very good telescope who stayed home?
And what if you drove your ship straight into a super-massive black hole?
Spend twice as long on boats though (32 years) and you can do about 10,000 light years.