Q about extent allocation and free space management with partitions

What happens if I have a 1G table spread over 10 100M extents and I split the partition in two? Does Oracle have to allocate 5 new 100M extents and the main partition now has 10 extents half of which are empty?

What happens if I drop the first partition? is Oracle capable of recovering the 5 extents as free space?

I'm asking because we're establishing purging policies and considering how to implement them. What appears to be the most natural way is to partition the table by day (nearly all transactions use records from within the same day) and keep a certain number of older partitions. Each day the lead partition would be split and the oldest partition would be exchanged out, exported, and dropped.

I'm just worried that while this seems like a nice procedure I'm worried that the lead partition will never recover the space being freed off the beginning by the splits. If it just keeps marching on is there any chance it will consume more and more space each day just as if we weren't purging?

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greg