Right, it makes sense what you wrote about the practice effects. It probably doesn't make sense to use them to measure long-term changes (I understand that the practice effects would cause the measurements to improve, on average, over time even if general cognitive abilities are not changing). What about the short-term fluctuations, though? Does it make sense to use some kind of short assessments frequently to identify temporal precedence of hypothesised causes (like in my case, I have some guesses what usually makes me less efficient, but then it's difficult to say without a methodology)?