If you've been there for 10 years, then the taxes on those options will murder you if you choose to exercise now. I think ideally, that you incrementally exercise over the period of time of your stay. Bigger risk since you won't be sure of the future of the company as you do now but the difference in the strike price and the value that you exercise would be smaller which would hopefully mean less tax. I think the idea is to exercise your options when the current value of the stock is not too far from the strike price granted.*

* I am not a tax adviser.