I suggest to use external EEPROM.
1. The flash in the NXP's ARM based MCU, only 100K erase/write cycles and 20 years of data retention.
EEPROM has 1M erase/write cycles and 200 years of data retention.
2. IAP only offers "Copy RAM to Flash" within 256 byte boundary. (depends on chip)
And the size of written should be 256/512/1K/4K (depends on chip)
You have to prepare the bulk data in RAM first.
3. the Flash memory must erase before writing. (of course, 1->0 is OK without erasing)
And the erase is based on Sector, the size of sector will be 4K or more (depends on chip)
So the internal flash memory is not suitable for small frequent changable data.
FYR.