They shot themselves in the foot with season 1 by giving us a billion different shorts, so not everything had to hit. To go from that to 8 or 10 short seasons, you really have to focus on quality and not all of them are gonna give you enough of that with the 10-minute run times.
i.e. The space chick with (lilo and) stitch was excellent. But the pastor and alien on the beach... that was just stupid; only got somewhat interesting at the very end but then it was over.