About 15 minutes, Rarity, and a hard to clean stain...

Spike and Rarity fuck increasingly hard for 14 minutes before Rarity, though holding herself back for a bigger and bigger 'finish' is totally overwhelmed by the sensations cumming from her pussy and screams like a banshee raking spike's back with her hooves, an act that only actually hurts HER thanks to his armored scales and triple row of jagged spines. After that Rarity kisses Spike and cranes her neck to whisper in his ear "Finish up now, fill me with your seed, it's not like we risk a pregnancy..." And Spike starts to really just FUCK her, not worried about getting her off any more but only satisfying his new-found carnal needs.

Just over a minute later his own orgasm floods his consciousness and he bellows a mighty roar that makes the chandelier jingle: as spurt after spurt after spurt of draconic cum fills Rarity's twat to the brim and then flows out of it onto her couch, staining the rich red fabric purple, a mark which will be HARD to get out, let me assure you, though Rarity, practical as well as generous, will simply reupholster the thing and keep the fabric as a souvenir and cum rag for her and Spike's further trysts.

As Spike's rod finishes spurting jizz at last and vanishes Rarity let's her sexual organs fade from existence again as well, smiling at Spike in the slowly fading glow of connubial bliss. "Ooooh, My dear sweet Spikey-Wikey, that was just amazing!" She coos, rubbing her hooves gently over his muscular chest scales. "You are just a natural at this, and I can't wait for tomorrow night!" Rarity croons even as she realizes that something is changing, a new event occurring, one she doesn't quite understand, yet...