I've been thinking lately about what is the optimal approach to these tactical problems for long term retention. There certainly are a number of options. There are Extremes ie: 1) De Maza Method doing each problem in a large complete set before returning to do them again. 2) breaking them into smaller sets and repeating them in a much smaller time period. Why wouldn't doing a single problem 7 times at one sitting before moving to the next problem work? What extent does review of problems one finds more difficult play? What extent does a deeper understanding a position play as opposed to rote memorization? What does the role of effort attempting to solve a tactic play in improvement?
Anyway, I continue to follow the advice from my Sharpen your tactics book. Keep Moving!