Depends on the manufacturer and what language you use with them. But you're right, usually they don't pay for expedited shipping. But they should!Personally I don't think it's a big deal as long as the manufacturer pays for the expedited shipping. It's a lot cheaper for a company to pay for international shipping than it is to open up new service centers.Good idea ... it would be awesome if they can do that ... and it will provide great credibility to the third party manufacturers ... but I don't think third party manufacturers will be willing to pay international shipping costs.
I think the best compromise would be if the manufacturer, after they've grown big enough, could open one service center per continent (so 4 service centers: America, Europe, Asia, Australia) and then the shipping would probably be faster and cheaper within one continent. But I don't know what's really cheaper Maybe that's what you meant but since many manufacturers don't do that it must be too expensive. I think they should then offer expedited shipping. I think: 5000 lenses sent in and $100 for expedited shipping = $500 thousand. Probably costs a lot more than that to open a new service center on another continent and hire all those new people and train them.
I don't think there's any truth to upgrading firmware or body screwing up the AF. Nikon and Canon also have nothing against third party manufacturers, either way they make a lot of money, especially since there will always be people like you who complain when they find out there's no service center at their doorstep. Some of those people probably run out and buy the equivalent Nikon and Canon lenses hoping that they will be magically better, so Canon and Nikon get their money and so do the third party manufactureres. Forums like this get the emotional fallout.