WDs above the gap are typically on-average   10,000K hotter than CV WDs below the period gap (almost certainly a consequence of higher time-averaged accretion rates of systems above the gap but possibly with system total age also being a factor). Since the white dwarf surface temperature is crucial for understanding CV evolution and whether CVs evolve across the period gap, the use of cooling ages and long term evolutionary model sequences with accretion (including the effects of nova explosions, @tow03) must rely on the empirical WD temperature of the photosphere in equilibrium with long term compressional heating from accretion. The work of @tow02 [@tow03] allows measured T$_{eff}$’s of CV WDs to be converted to the accretion rate per unit WD surface area averaged over the thermal time of the WD envelope.

Unfortunately, there are far fewer systems with reliably known WD properties above the period gap compared with below the gap, thus impeding detailed comparisons between the two groups. For example, among CVs below the gap, there are now roughly 20 systems with reliable WD temperatures but only 5 systems above the gap with reliable WD temperatures. The primary reason for this disparity is that in long period CVs with 