You'll hate the answer because "everyone is different" isn't what expectant moms want to hear! But, in reality, it's true! Diet, lifestyle, stress, sleeping patterns, and more can all influence the wonderful phenomenon of morning sickness.
For my wife, she had bouts of it for a few weeks and then it would subside. Only to return now and then as the pregnancy continued. I know that many don't expect it outside the first trimester but from watching Heather, I think it's more drawn on hope than experience.
I do know that we have lots of posts and even some articles on how to deal with morning sickness. Just in case you've tried and failed with other remedies.