they visit regularly for a while, then drift away, depending on the demands of their life. However, new members join, with some old and some new questions.

I agree it was always so.

But my impression has been that for the last few years; new people come, stay for a shorter time and don't some back.

In addition; the threads are shorter; there is less open debate; less to and fro and interchange of ideas. Basically, just less.

And when I went looking; the stats; every which way I viewed them, backed that up.

I'd love a couple of hours read-only access to the DB; then I could really extract some useful -- though probably depressing -- numbers.

But, those I've already looked at tell enough of the story to allow me to be confident in my conclusions.