One more thing @PAVB, if orignal poster's appl deletes 36 million records per week (though not practical) then i would guess/expect it would leave many free blocks for re-use. I suspect if oracle is using blocks efficiently in his case, either due to wrong settings in his environment or oracle is genuinely failing to re-use blocks or he is using IOT. IMHO IOT not re-using index blocks though we do delete range of sequence numbers (first key of IOT) which are older than some date.
"I Dont Want To Follow A Path, I would Rather Go Where There Is No Path And Leave A Trail."
"Ego is the worst thing many have, try to overcome it & you will be the best, if not good, person on this earth"