As far as I know, there is no limit on how many last calls one can book other than 52 weeks in a year, one's budget and vacation time!
However, cannot be rented nor bartered, but if all in the family who knows?
I do know Wyndham cancels overlapping reservations with no GC, but would have to check with RCI on their policy. Really don't think resort is involved. GCs are very profitable item for RCI!
I did a couple years ago and after conflicting double talk from VC decided a GC was not a big deal considering bargain on units! Plus you could get sick, etc. and have to cancel!
Definitely call resort a week out and ask for units next to each other or at least in same building!
Activity, WIFI, parking, recreation, taxes, safe deposit box, locker, etc. fees are resort unique and require a call to resort.!