I concur that this route is a business heavy route and that the R availability only increases when econ seats are full or oversold. It would be quite normal to have an R2 six months in advance while only 2 seats are actually sold. I'M on this route again this week and as Jasper posted, half of J pax book in advance and others last minute. Flight passes to south america book in M so availability is usually pretty good for a same day booking.