I fully agree with a lot of this. I've done the crock pot stuff, too. It does really help a lot of mixes, but over time, I became lazy with it and just mix up stuff I know I like in several 30ml bottles, so I always have some that's aged. Speed steeping works great for me, in a pinch, but time steep has been the best flavor producer for me. If you have spiced flavors, i.e. cinnamon, ginger, anise..., don't heat those. Kinda wrecks the taste.
Most of what I mix is well under 10%, so that shows you how different we all can be.
As far as shaking, I just shake it, store it, shake it some more later and then before I fill a tank.