Prevent slow Flush command


Using ALFAT firmware 1.08,
I have a meaurement device that needs to write about 4kb to the data card every second. I have learned from this forum (and experienced myself) that the flush command takes little more time. So I am thinking about using it less frequent while some data loss is acceptable. My questions are:
[ol]How often should I recall the flush command? e.g. when I continuously write data without flushing will all the data be lost with a power failure or is there some kind of built-in flush that writes the data back without intervention by the user.
When I write continuously data without flushing, will the ALFAT internal buffer overflow some time?
When I combine multiple write commands with one flush command, will the flush take signifiantly more time than applying it with each write command? [/ol]