Since the discovery of the first brown dwarfs (Tiede 1; Rebolo et al. 1995, Gliese 229B; Nakajima et al. 1995) the complement of identified brown dwarfs has grown to over 700. Yet our understanding of these cool objects is still somewhat lacking. Current models struggle to reproduce the observed variation in photometric and spectroscopic properties with good accuracy. What is needed is a way to aid and calibrate the models. This may be provided by 'benchmark' brown dwarfs, whose properties (e.g. age, mass, [Fe/H]) can be independently determined with minimal or no need to reference models. Such objects are not common however, and the level of accuracy on those constraints is not always high. We review the status of the current population of age benchmark brown dwarfs and summarise how these currently calibrate the Teff /logg /[Fe/H] parameter space. Finally we look at the potential for future discoveries that can be made from ongoing and near-future surveys.