Cant i just do this?

[GoW ViNtH3R]

I was thinking, is it possible to hurry through the game until the moment of no return. Then save in a different slot and start collectiong light seed's. After getting them all, couldnt i just load the other save file and get the achievement for completing it in less than 12 hours?

[tekkamaki]

I see no reasons why this couldn't be possible..