How about we stop basing it strictly on time all together? In my experience (And a few others here judging by posts) the shorter podcasts are better. How about we stop rewarding people who have nothing but time for rambling on about crap and go based on quality. Do like the graphics graders have done with video grading. Set a minimum time to get full marks (For podcasts lets say 15 minutes) once it's past that time it gets a guaranteed certain amount (Lets say 750k to keep with the current scale) then you add in grades for originality, quality and content. Each worth 50k per 1/10 grade for a maximum of 500k each. That way more people may be willing to listen to podcasts. Those who create GOOD podcasts will be rewarded, and the ones who are babbling for an hour just to get full marks actually put quality into their podcasts.

By my count the maximum you could get for this would be 2.25m as opposed to 3m maximum but takes 1/4 the time to record, but also rewards those who actually try while punishing those who don't.