I've been riding about 3 years and have worked on my cadence slowly over time to where my sweet spot is up to about 85. I can spin 90 but it just doesn't feel right yet. Friends who have ridden all their lives have told me they just cannot get to comfort at 90 RPM. I guess my point is not to question the benefits of spinning but to suggest that there is no single magic number. +1 to those who suggest enjoying the ride... and work slowly on improving your spin rate without obsessing about it.