You mean if you're still an employee? I've read their RSUs have 7y expiration, which is part of the whole Airbnb IPO problem because the ones from 2014 will start expiring next year.
But what's the window to exercise once you leave the company? I doubt it's until expiration.
RSUs normally expire only if there’s no liquidity event (ipo or sale) and once vested remain yours even after end of employement. Ofx that depends on specific contract
If these are double trigger RSUs they don’t fully vest until two conditions are met:
1) the usual employed by the company for a certain period of time
2) some qualifying liquidity event (ipo / sale)
This is to avoid employees needing to pay taxes after #1 even though the stock can’t be sold. However for tax reasons there has to be time limit when they either vest or expire worthless. Depends on which lawyer you ask how long that can be, but generally most are less than ten years.
But what's the window to exercise once you leave the company? I doubt it's until expiration.