Perhaps, it was just the excessive heat of summer or a long day at work but plodding through a book on the Slav and Semi-Slav last night finally brought me to ask the question: Is this necessary? The underlying strategy for Black in the QG Declined is to develop your C8 bishop quickly and to a good post. That's the problem Black has to solved in the opening. Otherwise, there are no big surprises, and that's why the QGD is considered a very safe opening to adopt as Black. So, trying to understand and retain the exact lines involved in the Central Variation and the Meran Variation is quite a task especially for someone who is already half a century old with a not-so-great short-term memory. Heck, I forget most of the theory just 24 hours later! Basically, with just enough opening theory stored in my gray matter, I find myself finding the best move in the opening that somehow controls or challenges the center, develop my pieces, maintain the initiative if I am playing White, minimize pawn moves as to minimize weak squares, and not lose a tempo. I find that this pans out to less mental work than memorizing specific lines of analysis that sooner or later escape my memory. Of course, the player with the better opening repertoire has the advantage over those who try to get through the opening sensibly. I reckon that the younger generation of players have a greater ability to retain this awesome load of opening theory, but for aging players like myself it has become a burden. I think the lesson learned here is to do all your work while you are young so that you can build the mental roadwork necessary to understand and retain chess knowledge with the minimum of labor. There is great wisdom in maximizing the benefits during the prime of your life. For me and in regards to chess, that's 30 years of age and below.