How old can a buying signal be before it's useless?

Genuine question for folks running outbound.

A funding round is all over LinkedIn within a day, so by the time your sequence goes out 50 other vendors have already pitched them. A new VP Sales feels useful for maybe their first 90 days while they're still deciding what to change. Someone posting that they're unhappy with a tool feels like it has a couple of weeks, tops.

But a lot of intent data I see is weeks old by the time anyone acts on it - at that point it's not intent, it's history.

So - what's the oldest signal you'd still act on? And has anyone actually tracked reply rates against how old the signal was when you reached out? Would love to see real numbers if anyone has them.