I can help, but u gotta edit the bad word above, use dang instead.
Each species and each male is different, some take longer than others due to their size and amount they hold. Also once they are in the position, both seem comfortable and probably see no need to move. As far as I know, there is any amount of reasons for the coupling to continue, as in.... fed well and in no hurry, maybe it takes that long because it is suppossed to.... Maybe they swell up like dogs do? Could be any number or reasons, and I am not sure any one has looked into it as being important., but if they did it would be Frederick Prete. Google his name and he has a good size book on mantis to read. If one can afford it, I find I can't!