My real question is why would some wireless devices loose touch with my in-home network. I understand interference, so no need to go into microwave ovens and cordless phones. But a networked printer and occasionally iPhones think they are connected; that is, they show the correct symbols and words in the appropriate settings, but they respond as if they are not on a network.

What corrects the problem (temporarily, which could be a week or a month) is to power off the router and then restart it.

Any thoughts?

What kind of router?

Usually, this is a bug in the router firmware. Asus routers in particular are absolutely notorious for doing this, to the point where there's a whole community of people who, totally independent of Asus, release their own modified Asus firmware that fixes some fo the most egregious problems. (I, unfortunately, have had an Asus router that had this problem.)

It's a Netgear dual band gigabit router.

I have done a recent firmware update, but the problem persists (before and after the update).