What happens to founders afterwards? Do they start another startup? Do they continue in a "job" (career)? Do they start from scratch or move immediately into a management position? Are investors willing to invest into failed founders? Are companies willing to hire them? Do they value experience (similarly to an MBA, or similarly to an employee, or not at all)? Maybe they get hired by VCs to either mentor other startups, or help decide if they're worth investing in?
The opportunity cost of starting a startup instead of continuing in your career can be significant (5+ years "lost"). I imagine Y Combinator and other accelerators/VCs have some relevant experience with their alumni to answer this question. Is there any data available, an article or similar?
[1] http://www.paulgraham.com/die.html