you are bang on with your question, for 24/7 use, performance memory is an absolute waste of funds...period. anyone arguing that point is either selling, advertising, or promoting memory with their best interests in mind, not a consumers.
DDR3-1600 at 8-8-8 (if not even less) is more than enough for any system (X58/P55) and anything over that is a huuuuuuge waste of money in a performance/$ ratio. for daily use, spend you money on SSDs, for gaming use on GPU, and for benching on everything
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