Do perpetual-style contracts expire?

In the case of any stock option associated with a merger in which the underlying security has been converted to 100% cash after December 31, 2007, the OCC will accelerate its expiration. The new expiration date for such options will be accelerated to the nearest standard equity expiration, unless the cash conversion takes place after the Tuesday within an expiration week, in which case the expiration date for all contracts not already expiring that week will be deferred until the following month’s expiration…

You can trade expiring options up to the end of the last trade date if the account has sufficient funds to meet both the real time and projected margin requirements.  The cut-off time for when you can open a new option position that expires the same day or the time you have left to close an open expiring option position depends on the available funds in the account.  Starting 2 1/2 hours before trading ends on the contracts last trade date IB's …

The US Stock options that stop trading at the end of the regular trading day on the 3rd Friday of the month (considered Monthly option) are settled using the Composite Close (CC) price calculated around 16:00 EST. An option is expired after the OCC completes it's processing. The standard expiration date for US Stock options is the Saturday immediately following the 3rd Friday of the month…

The only action one can take to prevent being assigned on a short option position is to buy back in the option prior to the close of trade on its last trading day (for equity options this is usually the Friday preceding the expiration date although there may also be weekly expiring options for certain classes). When you sell an option, you provided the purchaser with the right to exercise which they generally will do if the option is in-the-money at expiration…