That's what I don't get, why would it go down? Sure you get a pull for maybe 5-10 points.... not that bad, you recover that in about a few months...
maybe if you closed it right away but hold it and make sure you don't carry debt on it and it wouldnt matter much. Sure opening 10 cards might drop you 100 points, take 12 months to get back...
Not sure if it is rule but if your score is good, ie good habits of keeping debt down and paying it off, I get about 5-10 points a month back to my normal score. It's like medicine, you determine your normal and as you move away from it, your habits will return it back to normal, homeostasis... sure I'm not at 850 because I'm missing something, but I can get back up in 800s after churning given enough time