  The population of accretion-powered millisecond pulsars has grown rapidly
over the last four years, with the discovery of six new examples to bring the
total sample to seven. While the first six discovered are transients active for
a few weeks every two or more years, the most recently-discovered source HETE
J1900.1-2455, has been active for more than 8 months. We summarise the
transient behaviour of the population to estimate long-term time-averaged
fluxes, and equate these fluxes to the expected mass transfer rate driven by
gravitational radiation in order to constrain the distances. We also estimate
an upper limit of 6 kpc to the distance of IGR J00291+5934 based on the
non-detection of bursts from this source.
