There are two "mix" items I tend to make in cycles: scones and pancakes. Anytime I make a batch of pancakes I measure and combine the dry ingredients, including the baking powder, for two additional meals. I'll either bag the dry stuff in zip bags or put it in plastic containers. Make sure you mark it!!! (Yup, the voice of experience...) Same thing with scones. This way if I want to make a batch of either of them in the next month or so the dry stuff is already waiting. Never have had a problem since I use it up fast enough.
I don't pre-mix anything with a shortening in it like the Missouri mix has because I rarely use shortening. I sin and use butter.
Also, if a recipe has brown sugar as the sweetener I wait to add it in when I use the mix. If put in ahead the moisture in it is sucked out by the flour and the sugar gets hard and is very hard to remix with the rest of the stuff.
It does look like the Missouri Mix would work if you're looking for a substitute for Bisquick. Actually looks interesting enough I might give it a try just to have on had for shortcakes - it's strawberry season, after all. Thanks for the link sparrowgrass!