I am currently spinning my platform pedals at about 85-90 comfortably. I have found that it is easier (for me) to reach a higher cadence on slight inclines and in gentle head winds, and have therefore used such conditions to increase my cadence. Sometimes I can get a 20-25% higher cadence than normal if conditions are right, and maintain it for a minute or more.

On steeper climbs my cadence drop quite a lot (it is hard to keep the feet on the pedals while standing with a high cadence, and that is one of the main reasons why I plan to get some kind of clipless pedals soon).

/Csson