Lpc2000

Hi,
how effective is it to store user data (which can be updated 
relatively frequently) on lpc2138/48?
User data size is about 2K.
Data should be stored/updated within max 2ms.
Data is going to be loaded to RAM on power-up and operated from RAM.
 
As far as I understand, I have the following options:
1. Use external nonvolatile data memory (like spi flash, preferably 
with byte write capability) and update data in RAM and external flash 
on a fly.
2. Update data only in RAM. On power-down create sufficient VDD delay 
and store the whole RAM user data array to the on-chip flash. Not 
sure how long storing of 2K of data will take. And I believe that 
according to one of the previous discussions I can write data to the 
on-chip flash providing interrupts are disabled (?)
3. Update data in RAM and in on-chip flash on a fly. As far as I 
understand, there is no byte-write provision for flash in lpc, so I 
will need to save a page - 256 bytes. The question here is, of 
coarse, time to store a page, and, second - flash endurance. How many 
times can I write to the flash (I couldn't find information on that)?

Will appreciate advice and considerations.

Gennady