Hmm….
I definitely do see where you're coming from--Oda is constantly alluding to Luffy shortening his own life to be able to continue towards his goals or to protect the people close to him. However, there were also a couple promises he made to meet up with several people that he met along the journey, and Luffy isn't the type to break promises.
I agree with your point on Luffy's character and his thirst for adventure. He'd probably want to continue on a new adventure not shortly after finding "One Piece".
Maybe it's just wishful thinking (I won't deny that Luffy's death is a possibility), but I believe that "One Piece" isn't the ultimatum of adventures. There always can be more, always! Part of the fun is going out to find it. Luffy wouldn't be an adventurer if he thought he'd done everything after just one, no matter how crazy the first one is.