The reason you have a slow save time is that the CPU is servicing the IPFIX and HAL process most likely. If you type "top" at the CLI you can monitor the % CPU utilization and confirm. Be sure you are using the latest code of 15.4 or later for IPFIX as there are some specific improvements that have been incorporated. The switch will function fine and pass traffic without issue as the IPFIX flow information is created with the ASIC, the CPU use is a function of how XOS handles the flows and checkpoints within the OS. Let me know if you have any other questions.