Whatever NSE decides to keep between Nifty/BNF should be made to expire every Thursday of the week, the one not choosen for weekly will expiry on the Tuesday of last week of the month.
Now the next most actively traded contract (~10% of average Daily premium turnover) after Nifty and BNF for NSE is FinNifty, this should expire on the Tuesday of the third week. After FinNifty comes Midcap nifty (~5% of average daily turnover) which should expire on the Tuesday of second week of the month and at last recently launched NiftyNext50 should expire on the Tuesday of the first week of the month.
This way, NSE should be able to retain a good number of its traders from switching over to BSE’s Sensex and more importantly for us traders it’ll be one more expiry every week than what SEBI wants us to have.
It’s not necessary for a Monthly derivatives contract to expire close to the end of the month for it to be called a ‘Monthly Contract’, for example CrudeOil monthly contracts on MCX and CME expire around 20th of the month.