So if you write accelerometer data as 16 bit values so you don't lose any information that's 6 bytes per reading, so 15,000 samples - and there are only 3600 seconds in an hour.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
It might be worth looking at http://www.espruino.com/Data+Collection#flash-memory for how to store data in flash memory vs RAM. It also comes with an example of how to output the data as CSV.
If you write a 'minimal' Puck.js build to your Puck (https://www.espruino.com/Download#puckjs) you get more free flash memory - I think around 90kB.
So if you write accelerometer data as 16 bit values so you don't lose any information that's 6 bytes per reading, so 15,000 samples - and there are only 3600 seconds in an hour.