Churning my cards is IMHO the best way to get AA miles at a crazy rate. You can get 100k+ per quarter if you really max it out. The coins gig seemed better for some folks but I don't have the time to find banks to deposit hundreds of thousands of coins each month

The impact on credit is minimal and frankly at 800+ I think you have nothing to worry about. Fact is 750+ will put you into the top bracket, so getting to 800 just earns bragging rights. You get the best mortgage rate at 750, you don't improve at 800. For someone looking to buy a house who has a score < 800 I would say wait till your moved in, then start burning straight away. For other forms of credit I'd say as long as you start out > 750 your fine.

Opening/closing accounts won't have a huge impact on your score anyway. I can tell you from experience using up your credit lines is far worse. Listen to FrugalTravelGuy when he says don't use more than 50% of your credit lines. In fact don't use more than 35%. That way you keep the hit to a minimum.

Even having said that... if you do go over those suggested limits... if you pay it off then your credit score bounces back immediately. Last year my FICO went down to 650 as I had a 20k balance on a 26k Amex card along with about 10k across 3 maxed out 0% interest cards. I wanted car financing so just paid the whole whack off and within about 5 weeks once everything was updated on credit reports my FICO went up to 740ish. Just opening and closing accounts will not give you that kind of volatility...