24 hours later update
after taking some time alone with her, he mounted her again in a variety of positions. this included her first time being "reversed": he laid her on her back, kneeled backward on the bed and fucked his thick black cock into her. at first she said "i don't think this will work" and then as he managed to wedge his cock inside quickly corrected herself adding with a playful, girlish giggle "guess i was wrong!"
our time being limited, i suggested that he come all over her pretty, smirking face. he has mentioned wanting to do this before, but is actually quite a gentleman, and wanted to make certain we were both good with it.
Of course, she loved the idea and kneeled in front of him, alternatively sucking and having him jerk his cock over her head. to further encourage his spurt, she started to lick and suck his balls, perineum and upper thighs. this is something she's never done for anyone else, and he takes incredible pleasure in feeling her cat-like tongue all over his groin.
after a few minutes, he announced that "Baby, here it comes!" she lifted her head submissively- still wearing her collar, after 2+ hours- and i could see the thick white sperm oozing off his cock. then, a huge jerk and he unloaded completely, covering her eyes, nose and leaving a long drip hanging off her chin. it was, to say the least, spectacular. i watched as she greedily took the head into her mouth, then watched her cheeks expand as she drank down as much of his precious juice as she could. he gently held the back of her head, wiping the cock across her face and smiling down at her. they stayed this way for several minutes, very intimate and intense.
will post more, much more actually, about the morning session and in response to our other responders. thanks so much for all your input.