Michelle, I've found with my dogs that a good "stay" is the hardest of the basic commands to train. But once they idea clicks in their head, they're usually quite reliable. You've done a marvelous job with Precious - in a stay, she's patient but excited and focused. That's exactly what you want her to be!
Have you thought about training her for obedience trials? She'd be wonderful at it, I'll bet. But I guess you're too busy with school and such. I think it's great that you've built such an enviable relationship with Precious. You are so devoted to her. That's what dog ownership would always be like in a perfect world!
Much love to you and Precious!