As someone who has been fired and given 90 days to cough up a few grand to exercise, it sucks. Unplanned change of employment is a turbulent financial event and the last thing you can wrap your head around is whether the lottery ticket is worth it. Add in the feeling of distrust that often follows getting fired and it's really hard to objectively evaluate the company and its position.

I ended up not exercising. Still not sure if it was the right call.

Most companies have a clause that states options expire on termination for cause.