> The Xbox360, PS3 and Wii have all (AFAIK) gone well beyond the lifespans of their predecessors.

    PS1 (Dec 1994)
    PS2 (Nov 2000) = PS1 + 71 months
    PS3 (Nov 2006) = PS2 + 72 months
    today (Jun 2012) = PS3 + 67 months

    Gamecube (Sep 2001)
    Wii (Nov 2006) = GC + 62 months
    today (Jun 2012) = Wii + 67 months
    (Wii U already announced for later this year)

    Xbox (Nov 2001)
    Xbox360 (Nov 2005) = Xbox + 48 months
    today (Jun 2012) = Xbox360 + 79 months

Only one of these is significantly beyond the lifespan of its predecessors, and that's in large part because its predecessor had such a short lifespan, by industry standards.