Wouldn't that only be an issue if a company offers NSOs instead of ISOs? What I've seen in the past is "here's some ISOs, they automatically convert to NSOs 90 days after you leave." That way you get all the benefits of an ISO (tax on sale) while you work there, then all the benefits of an NSO (doesn't disappear in a puff of smoke at day 90). Seems like strictly a win, regardless of company phase.