How long can I log on to a 4GB SD card?

The amount of space required for one day’s logging at 1-minute intervals is 1 kB. So, on a 4 GB SD card, one can log for more than 8 years.

At ten-second intervals, it will be, six times more data, that will work out to about 4.5 MB per day. So, one will be able to log for about 1.3 years on a 4GB SD card.