I have recently used Skinners ruff and ready, and Autarky, and have been very happy with them both.  Dogs love them both too.  I can't really decide which one is preferable.

I know the general idea of feeding dogs is to stick with one type of food, but I was wondering if I could alternate between the two brands, changing approx every six to eight weeks. 

Dogs are Labs, so have cast iron stomachs, but the change would still be done gradually, mixing old with new.  Is this a good idea, or should I just pick one brand and stick with it? 

Thanks for your thoughts.

there is no problem alteranting the food every 2 months or so we have to do this with our dogs as they do get a bit bord with the same food evey day

There is absolutely no problem in using the two brands side by side - or three brands/four brands if you like.