Hi curryhell, yes i did once think the same. However i have let base mature for several days and it does get i iny bit nearer the bir taste, as the onions begin to ferment. but not significantly better to be worth repeating.
It is a fact restaurants are cagey about revealing there base sauce recipe. i think they will provide the spice mix at a push, but not the base sauce recipe. This was my experience anyway. I must ask to get a demo at my local of them making a base sauce. They never said this would be a strict no no. It may be a bit odd though turning up in the morning !!