Know-How Exchange : Research/Metrics

The answer probably differs for every industry and every situation. If you're selling a high-ticket item and there is a long sales cycle, then letting a lead sit untended for an extra week or two probably isn't so terrible. If you're selling an "Act Now!" item, even a few days might make a difference.

It also may depend on the copy from which you solicited the lead. Does it suggest "someone will get right back to you?" Setting realistic expectations is probably the best way to handle it.

Is there some way to automate a series of "touches" to keep your leads warm while they await follow-up?

If this is a critically important issue, it's probably worth investing in some primary research. I'll bet a creative market research professional would be able to come up with a way to develop the metric you seek. (Let me know if you want a recommendation.)

That depends on when the lead came in, who it was directed to, how much detail the lead gave (or was required to give), and how much the sales person knows about his or her profession and the needs of the customer.

This might help:

https://blog.hubspot.com/insiders/why-your-b2b-lead-response-time-is-killin...

When you say, "will become less responsive over time", do you mean days or weeks?