mineralogist,
The idea that God would wait until Adam was 30 years old is a good one. But 30 years after 1975 is 2005 and thus the end is next year year .
However, the Watchtower is good at stretching dates and could perhaps state that since Adam's life-expectancy was eternal there was no need for God to rush things. Afterall, some of Adam's early descendants did not have children until their 70s or 80s. That way the WTS could keep the 7000 year creative day, and Eve's creation date could decades after Adam, even a century if the WTS survives into the 2070s.
3rd
PS According to Genesis, Adam was 130 years of age when he became father to Seth. Considering that Cain and Abel were born and appeared to reach maturity before Seth was born and that Cain had a sister to marry there is an upper limit to the time between Adam's creation and that of Eve...that's assuming that the Genesis account is history and not myth.