I will only arrange insurance when I apply for the COE (or whatever it's called now) and I presume that would need to be for 60 days along with the SHA+ requirements and a return flight. Luma quote 3,900 baht for 60 days. I didn't need to show a return flight, and just booked a room (which I can cancel) for the first night. The £30 fee is less than the 1,900 baht 30 day extension (only pennies difference I know), but 90 days in total is now an option.