Your two lines are apparently on different time tables. That is interesting. Here is the way the contracts work.
12 month contract means your contract will be up after 12 months you can upgrade after 10 months and you do not get any new every 2 credit.
24 month contract means your contract will be up after 24 months but you can upgrade after 12 months with either a 1 year contract or paying a early upgrade fee (I have never had to pay that so this must be fairly new or I have just been lucky) or you can upgrade after 20 months with a New Every 2 credit (beginning this year that is 25 for low end rate plans and 50 for the higher ones).
Secondary lines on a family share plan are not eligable for early upgrades or for new every 2. They can only upgrade for the contract price of their choosing at the 10 month for a 1 year contract and 20 month for a 2 year contract. The only exceptions I know of to this are exceptional groveling at the right store on the right date to the right manager, and if you have had multiple returns/exchanges or warranty claims in the time you have had it for legitimate manufacturer problems. Sometimes those two things combined can make a pretty good case for an early upgrade to a secondary line. I wouldn't count on either working though. My E815 was exchanged more times than the Flu in a Kindergarten but I had to wait out my contract.
Since I put my wife (then girlfriend) on my plan I have always waited until both phones were eligable for upgrade. Sometimes that was really frustrating for me since I tend to get frustrated with my phone after about a year or so and want some new fancy something or another and I could do it but in order to get her the best phone possible we wait so I could use my New Every 2 and we could get whatever was the best BOGO or use the NE2 on her phone so she would have what she wanted and I could get what I wanted. The times that frustrated me were the times that I waited so we could do that and we both wanted phones that were free with new contracts so we didn't have to use BOGO's or the NE2. That felt like a waste. When I was single I would early upgrade almost every time for whatever feature phone struck my fancy and/or was free with new 2 year agreement.
