I’d say one to five years beyond a Master’s degree would be a fair measure. Successful grads who have gone to Wall Street into finance, whether with an MBA or a couple of degrees in math or physics, should be on the ramp toward $1M-per by then.
We’re not talking the bulk of young grads, but the high-end potential. Of course, become a Silicon Valley whiz and there’s great potential there too.
Undergraduates who major in business admin on average aren’t nearly the brightest, which is the reason, rather than their choice of major, that they don’t tend to become corporate CEOs down the line.
I would say (and have experienced) that a Master's degree is not needed to be quite successful with an engineering degree.