Desmond, Hawking, being different and changing things

[Lurcher]

I just re-watched 'flashes before your eyes' and noticed that Des was on the brink of changing the future, until Eloise Hawking showed up to stop him. Had she not been there so conveniently, Des would have taken the ring and married penny, preventing him ever going to the island. Also i'd forgotten that he got spat back out of time the moment he realised 'I can change things!'. This, combined with Daniel saying he was different, leads me to believe the 815ers can try as they might, but they won't alter the future until Desmond turns up and does it properly