Optimal Technique for Table Partition (Maxval) Removal

In our one of our Database we have several partitioned tables who have a final partition with MAXVALUE; hence all current data entries are flowing in. The tables are date range partitioned tables. We wish to remove the maxvalue partition, implement Oralce Automatic Managed Partitioning, while preserving the data from the MAXVALUE partition (implemented a few years ago).

Traditionally, splitting the MAXVALUE partition into defined date partitionsdropping the MAXVALUE partition setting table with partition interval (here monthly)

is used. However the challenge is the Maintenance Window timing (a few hours). The above can be split into multiple maintenance, but with several years of data this will take some time.