Thanks to Al, Eric & oec2000, your insight is very useful.
I have had several of my puts assigned. Usually when the market is tanking. Lesson #1: keep the cash on hand! The margin will probably disappear at the same time that you need to buy the shares.
The market usually bounces back fairly quickly, so once the initial cash drain occurs, there is usually an opportunity to offload a portion of the position at a profit. This however does not seem to last very long. Lesson #2: don't get too greedy. Take the easy return and leave the balance to others.
Eric, I find your strategy with options intriguing. It appears that the puts are a way of getting a yield on your cash. The re-investment of the yield on cheap calls is simply an investment (in this case of the yield). This works if the puts are not assigned. I am guessing that your puts are significantly out of the money.
I was looking at a much simpler view of buying using puts. If assigned/exercised, then the desired discount was achieved and the shares are purchased at a discount. If not, the cash is yours to keep. In this environment, there are so many opportunities that collecting the premium creates new opportunities in the future.