One thing I’m learning from this - or should I say is being reinforced - is that the time really is just a marker to compare other data against. It’s almost useless as the ratio increases and/or the flow exceeds 5ml/s unless you’re tracking in tenths of a second, which I don’t believe many (most?) people are.
It can certainly tell you that something is ‘way out’ from expectations, but then you probably don’t need a time to tell you that. Otherwise, taste is much more of a control mechanism.
As a marker, looking at pre-infusion times, time to first drip, etc. are all useful indicators of consistency, but beyond that it’s just another data point.
I still time my shots, and most land somewhere within 22-38 seconds, but that’s simply correlation rather than causation. If a shot is outside of that range, or towards the edges - ignoring every other reason - I may make a change to see how it could improve, but not on the basis that what I have is wrong. I’ve learned so much by reaching a ‘tasty’ shot, and then constantly experimenting with the other variables (temp/grind/dose/yield) in both directions, to see where it takes me.
Maybe when I’m ‘experienced’, I’ll stop worrying about the constant dialling-in, and just be happy when I hit the first ‘good’ shot. But then, why don’t I just buy an automatic machine… the journey is now the main reason - great coffee has become the conclusion.
EDIT: Today was a great example - I (foolishly) cleaned my C40 at the weekend, even though I’m not changing beans, thinking that the ‘clicks’ would be a good enough calibration. They weren’t and so the first shot at the ‘same’ settings gushed. Of course, I didn’t need to see the time to know this (45g/18s) as it spattered everywhere as well due to the flow. I knew from the ‘difference’ that something was wrong, so then adjusted my grind and the next attempt was back to where I expected. Not using the time as a fixed requirement, but as a marker to where my other settings have been landing.