Is there a way to SubPartition?

Is there a way to use multi-level inheritance to achieve sub
partitioning that the query optimizer will recognize? With our current
application design, we would need a partition for every other day for
18 months which will not perform well. The reason we need so many
partitions is that we can't afford to vacuum the active partition (750MM
inserts + updates per day is the performance requirement for 12 months
out). After it's a day old, there are no longer any updates or inserts
and we can vacuum it at that point. If multi-level partitioning
worked, we could solve this problem without changing our code. Ideas?

-Jerry