Flux viscosity difference between 2019 and 2025 batches

I keep a log of every rework job I do, and I noticed something odd going back through it. In 2019 I was using the same brand of no-clean flux pen I buy now, but the tackiness and spread are completely different. Old flux would hold components in place for a full minute before reflow. New stuff dries almost instantly, which is fine for tiny SMD work but a pain when I'm positioning a 48-pin QFP. I think the formula changed around 2022, but the label still says the same part number. A fellow tech in Austin told me he saw the same shift with his stock, so it's not just a bad batch. Has anyone else compared their old flux pens to new ones and noticed this? Or am I chasing a variable that doesn't matter once you hit the hot air gun?

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