$50 Multi-Line 8GB Bonus Data Question

I signed up for the prepaid $50.00 8GB with the 8GB bonus with autopay a few months back. I have a friend who signed up for this as well. If one of us invites the other to a multi-line plan will both of our plans stay the same and maintain the 8GB bonus data as long as autopay continues? I know one of us will lose any rollover data and we should wait until the day before one plan renews, but I just want to make sure we don't lose the bonus data as well. Saving an addition $10 is nice, but it is not worth it to us right now if we will lose that bonus data.