If you want numbers:Does anyone know what determines how long a sex scene is? It seems that most of the random npcs I can have sex with for as many orgasms, then there are others that are done after their one orgasm. So this leads to me not gaining any arcane essence from them, not that I need it or can't get it from other npcs, some are slaves or people that I invited to the house. So far in my "testing" it does not appear to be linked with the level of corruption or lust of the npc. I am not sure if I triggered something by at one point choosing to quick sex the npc, and now they are stuck like this?
Non-demons need one before they end, Half-demons need two, and Demons need three. The aforementioned Object of Desire perk increases each threshold by one (So two times for non-demons, three times for Half-demons, and four for Demons).