I re-read your message. Is it true that your numbers are 3-6 min per PARTITION and 25-30 min per PARTITION? or is this per cube? This would...

I had a similar problem several years ago. We were creating 16 partitions a day for about 3 months of data - so about 960 partitions, similar number of...

Yes, this happens to me too...  I'm desperately looking for an answer, so I'll find one if you haven't yet (years later)