in terms of sucessful eras of the band it seems there are three studio album cycles in each era that was popular before another new member joins with journey starting with...
gregg rollie era starts...1975-journey,1976-look into the future,1977-next
steve perry era starts...1978-infinity,1979-evolution,1980-departure
jon cain era starts.........1981-escape,1983-frontiers,1986-raised on radio
then you had the 1990's studio album trial by fire then...
steve augeri era starts...2001-arrival,2002-red 13,2005-generations.
maybe 2008's revelation is the start of a three album run by arnel...