  We explore different evolutionary scenarios to explain the helium deficiency
observed in H1504+65, the most massive known PG1159 star. We concentrate mainly
on the possibility that this star could be the result of mass loss shortly
after the born-again and during the subsequent evolution through the [WCL]
stage. This possibility is sustained by recent observational evidence of
extensive mass-loss events in Sakurai's object and is in line with the recent
finding that such mass losses give rise to PG1159 models with thin helium-rich
envelopes and large rates of period change, as demanded by the pulsating star
PG1159-035. We compute the post born again evolution of massive sequences by
taking into account different mass-loss rate histories. Our results show that
stationary winds during the post-born-again evolution fail to remove completely
the helium-rich envelope so as to explain the helium deficiency observed in
H1504+65. Stationary winds during the Sakurai and [WCL] stages only remove at
most half of the envelope surviving the violent hydrogen burning during the
born-again phase. In view of our results, the recently suggested evolutionary
connection born-again stars --> H1504+65 --> white dwarfs with carbon-rich
atmospheres is difficult to sustain unless the whole helium-rich envelope could
be ejected by non-stationary mass-loss episodes during the Sakurai stage.
