How to plan for/manage/reason about volatility in tech careers

I'm in my early 30s, the point when careers start to diverge. Spent my 20s going to college, working at Microsoft, founding a startup (acquired, not much personal return), and then working at a someone else's startup for 3 years. I was reasonably successful and happy doing all of them.

Many of my friends work at bigco tech jobs (Google/Apple/fb) and make $300k/year or more (this is not normal, these are exceptional people, many with PhDs from top-5 CS/ECE schools). I'm trying to compare this lifestyle to the spolsky/basecamp/bootstrapper path (for myself) and have realized a few things:

(a) Absent some sort of acquisition, there is a real shot of earning 3-4mil/pretax over the next decade at a bigco job. There is no viable path to do this out of revenue from a smaller, slow-growing business, esp. with employees involved. (Feel free to tell me I'm wrong about this, but explain why.)

(b) However, the mid-career options after getting into a bigco are...questionable. Spend your late 30s/40s as a middle manager whose career is strongly tied to a single company. Your tech skills atrophy because you spend your whole day in meetings and politics. You lose track of what's really going on outside the firm. And, you're one reorg away from being laid off, even though your employability somewhere else declines.

(c) It's an interesting problem through the lens of finance. The small business path is low-volatility, the bigco path has more volatility than people realize. How do people think about this? Do people in their 40s in management save a lot so that when a major dislocation happens, they can weather it? How do people do this in the Bay Area, with a 6k/month mortgage and tons of debt/school payments/other expenses normally incurred with a family? What's the plan?

Bottom line: if you work at a bigger company, you're going to have a bad year at some point (or 2). How do people plan for/account for this in career planning?