The bitstream option BITSTREAM.ENCRYPTION.KEYLIFE defines the number of encryption blocks per key. An encryption block is 128 bits (four 32-bit words).
Fewer encryption blocks per key offers greater security but exponentially increases bitstream size and therefore configuration time.
Selecting a value such as 1,024 or higher increases configuration size by about 15%, a value of 64 can increase bitstream size by 50%, and a value of 32 can double the bitstream size.
Attached is a spreadsheet that you can use to estimate the bitstream size when selecting different values of encryption block per key.
This estimate will allow you to calculate configuration time and also storage requirements.