For the most part, and backed by no data whatsoever, I think a good amount of folks juggle multiple things at a time, with each moving piece reaching its milestone and/or finish line one parallel to the other. I’ve referred this to the Gantt Chart of Life in previous posts, but thought of another way to capture it in writing — “in aggregate”.
Let’s say you’re learning two new languages, Cantonese and Farsi… the amount of studying it requires to have a strong grasp of them (ie. using either language conversationally) might be really intense. But if you keep at steadily, over time, you’ll become trilingual. In aggregate, all those efforts will have paid off. That actually just brought me to another anecdotal analogy — single-, dual- and multi-core processing. Oh my, the various places I can take this bloggity… so riveting! 😛