[jayp]

A 10-year exercise window has to be extremely rare to the order of non-existing in SV startups. Maybe it's picking up stream since the article was written and I am not aware of it. Can an employee vouch for his/her employer (company) that does this? Do more recent YC companies do this?

In fact, even Quora hadn't actually implemented a 10-year exercisable window by the time (or right before the time) Sam's article was written: see comment at https://news.ycombinator.com/item?id=7610668. Note that the article simply mentions it as an idea; not as an ongoing implementation. I wonder if it is now actually implemented at Quora.