I've been going with China Post Registered. (I ask for registered each time). That method has resulted in consistent 12-15 day arrivals and the hang up has been US customs. It sits in US customs longer than anywhere else.
So far shipping times from China to the US have been from 4 to 6 days, with US customs times of 5-7 days and US postal accounts for the other 2-3 days. That's how my last 8 orders have gone and that's from March to now.
Right now I have one sitting in Customs in NY, but I don't expect to see that one for another month, with the hurricane.