i think that you need to ride more intelligently, not necessarily longer.
you only need one of those long rides once every 2 weeks. other than that, i'd focus one day on speed, one day on intervals and one day on easy spin.
if you read articles by guys who have done RAAM, these other shorter rides are important, not just for your fitness but for your sanity.
essentially your ride is broken down into 4 x 35 mile rides (you can break it down into any managable sections)
speed is important, but only if it incorporated with endurance. so the speed, interval, on bike recovery (slow spin) are equally important.
then as you progress, combining all these disciplines on the last long rides just before your event should cap off a great training period.
come race day, there might be unforseen winds or weather that might prevent you from attaining your
PR, but it won't be for lack of preperation.
and try out different nutrition ideas, both on and off the bike so you aren't limiting yourself in that regard.