I average 78 cadence over a 30 kilometer ride of relatively flat terrain. The average factors into time I am not spinning so my moving average is likely in mid 80s or so. That is a comfortable cadence for me now but I built it up from mashing in the mid 50s. Get a computer and track it. Shift down - its faster - doesn't make sense to me - but its faster.
Most important have fun b/c if you don't the bike will gather dust.