The way this is policied is the "Not valid before" date on the last international coupon. If you have a paper ticket that hasn't been reissued this is not an issue. On an eticket I can see that it might be. Make sure that the PNR is well-annotated. I would be more comfortable if the RTW desk (or whoever set this up for you) was going to be open at the time I was checking in for that last international flight so that I had someone to call in the event of any problems. If that isn't going to be the case then it might be worth trying to get the RTW desk to send you an email or something explaining the situation and confirming that it is OK.