Working with a 1.060 original gravity wort, mashed at 152F, and using the WLP565 Dupont yeast (that is known to stall), when should the brewer investigate if adding a secondary strain of yeast will be required? Is there a rule of thumb or accepted practice that suggests if X% of expected attenuation is not complete by Y days, then attenuation will very likely require a very long time?
Of course there are various options for the brewer, such as raising the fermentation temperature, removing back pressure, or simply waiting for the fermentation rate to start again. But this question is about the earliest point where the brewer might know with reasonable certainty that action is going to be required to get the beer to quickly completely attenuate, and what to do at that point.
The default process is to take multiple gravity readings, and when the slope doesn't change from one measurement to the next, then it's time to take action. But is there a way to "know", right away, by taking just one, properly timed measurement?
With this yeast, there are many brewers reporting "stuck at 1.030" or "stalled at 1.035", which are roughly only 50% or 60% of expected attenuation, but it's usually after a few weeks of frustration and multiple measurements.
Given that in a typical fermentation curve, the majority of the attenuation occurs in the first six days, when should I take the measurement that will indicate a stall, and above what value would indicate a stall?