It's not idling related IMHO. Too many cases of engines at high miles and high idling and 0 lifter issues. We also have enough of cases of lifter failure with low idle hours.
The lifter failures need engine runtime to happen (right, it's a wear item and it needs to run to wear). So when enough run time occurs, either by driving or idling, a poorly hardened cam or poorly manufactured lifter will destroy itself regardless of RPM level. If its running, it'll wear. But it's not strictly related to idling. In other words if you have the junk cam/lifter it will eat itself when either enough idling or driving occurs, but if you don't idle it you'll still get the failure just with more drive hours instead.
Here is a great example: 603,000 KM (375,000 miles), 3700 idle hours no failures at this point:
www.reddit.com
Example #2 would be "truck central" on YT, about 250,000 miles with hard towing and 1600+ idle hours, dealer oil 5w-20, no failures yet.
There are many other examples, I just don't remember them all.