We discuss brown dwarf properties that can be measured from current and future deep surveys, and how fundamental parameters, such as the mass function and formation history may be measured. As well as the possibility of finding new populations of benchmark objects that can be used to refine the calibration of ultra-cool models with new precisely measured properties. We also describe our ongoing searches for benchmark brown dwarfs, and discuss our first measurement of the formation history in the sub-stellar regime using data from the UKIDSS Large Area Survey.