Joanna, you have nearly five hours at LAX--more than enough time no matter how far you have to go to change terminals. And also more than enough time for your bags to get from one flight to another--you don't want them to get moldy ;) ! Don't change your flight--more than five hours at LAX would be awful ...have you seen the Tom Hanks movie "Terminal"?
Maria, our flight time to LHR was changed so that we only had a little over an hour at Heathrow--definitely not enough time there. So we moved our flight to Nice and now we have about three and a half hours to change flights. I'm really comfortable with that.