As has been posted before, if you are on separate PNR, or if there are more than 2 on a PNR, and you are able to get a CS agent to put you in E+, it only seems to stick if there are NO schedule changes or equipment changes or anything. Any sort of change, however small, seems to result in the E+ "challenged" to be bounced back to never-never land, otherwise known as 55E.