There are so many variables to saponification (your formula, the temperatures your batch achieves and length of time at higher temperatures, gel/non-gel, how long the ingredients are mixed/blended, how well the ingredients are mixed/blended, etc, etc, etc.). I personally don't push the lye solution envelope far beyond 40%, more often using 33-35% to ensure the lye crystals/flakes remain in solution without becoming supersaturated and potentially precipitating out of solution. IME, using a water discount does several things. First, the freshly cut bars are closer to their final weights they will be after adequate curing. I have weighed several bars from batches with different water discounts over the course of several months. Those without water discounts lost more water weight over time; some actually achieved the 'shrunken head' look at the end. Second, stronger lye solution concentrations help to achieve emulsion and trace more quickly. This is especially important to me when making castiles or bastiles that are high in slow-tracing oils such as Olive. The combination of higher temperature and stronger solution saves me a LOT of time getting a stable emulsification and thicker trace without burning out stick blenders. There's no substitute for time.