Tech doesn't automagically improve with time. It does with effort (& insight). Can't just wait 30yrs & expect tech to have progressed. It may have regressed! Likewise, there's no a priori firm limit besides physics that stops 22nd Century tech being developed far sooner.

@Robotbeat The limit is brain power to development and maintain a certain level. Apollo being an example of assigning brain power at the expense of everything else, it wasn't maintainable. It will be interesting to see if AI helps or creates a larger load on the human substrate.