I choose to write deep in the money calls because it requires...

I choose to write deep in the money calls because it requires less margin, less contracts need to be written and therefore risk is lower. It is safer than buying calls because if NAB stays put I still make money on the written calls, whereas I lose the lot on bought puts.

If I wrote Aug calls there would be very little time premium and the probability of getting exercised would be unacceptable. Therefore I go to Sept where the time premium discourages exercising.
I am expecting major carnage in the banking sector, and writing 3450 calls is not very profitable. Say NAB fell to 3450 at expiry, I make a measly 50c. But with the 3000 calls, I make 9x as much.