I do it the most of the time, but not all. depends on what I'm mashing, and how I'm mashing it. For 'standard' brews with 'standard' mashes, I don't bother anymore, but if I am doing a short stiff mash (specifically for increased dextrins, which is happening more often. Jump mash v2 is happening tommorow night), I want to mash only as long as required for conversion, and without iodine testing, this comes down to guesswork.