The ISO -> NSO switch can have severe tax consequences for the employee. Even if your company doesn't expire your options in 90 days, consider exercising within 90 days anyway (and talk to a tax lawyer, etc.).
One not-as-obvious reason why companies are reluctant to set long expiration dates on options is because it means former employees take up space in the cap table even if they have no intention of ever exercising that option. The company essentially has to treat those shares as having been purchased, without having received any cash for said purchase. Cap table cruft can make it harder to negotiate subsequent funding rounds.
One not-as-obvious reason why companies are reluctant to set long expiration dates on options is because it means former employees take up space in the cap table even if they have no intention of ever exercising that option. The company essentially has to treat those shares as having been purchased, without having received any cash for said purchase. Cap table cruft can make it harder to negotiate subsequent funding rounds.