I can only say that in my life time of watching the Wallabies (the early 1980's until now) we've been competitive almost the whole way through. We still are actually. It's just that we're in a trough right now that will take some effort to get out of.
I guess it depends on your definition of competitive, the win loss ration since 1980 is worse than 2-1, and that includes the era where the Wallabies could claim to be more than competitive - '88-'02. Of the games they have won in the last 36 years since 1980, nearly 25% of them were in that 4 year window.
In the last 13 years the Wallabies have won 6 games and lost 29 - thats sort of outside my definition of competitive!
In my lifetime I think a reasonable argument could be made for the Wallabies being competitive from the late '70's until the early noughties, so to go back to Pedrocolis' comment that he "grew up in a rare period of Wallaby competitiveness" and my throwaway line that he "must have grown up very quickly" - a closer look shows that his comment is accurate and my cheap shot just that!