I noticed you didn't refer to measuring chain link wear. Any comments on that?
I measure chain wear with the (less than ideal) Rohloff tool.
Measuring is mainly useful on the family Bromptons, a Chainglider is not possible on these, and with small wheels the chain picks up more muck and wears faster than on other bikes. So I replace the chain, together with the very cheap rear sprocket, between 0.75% and 1% measured wear to try and save wear on the chainring.
The same applied to derailleur geared bikes when I had them, except that I tried to replace chains at 0,75% measured wear to save the relatively expensive freewheel or cassette. These generally lasted for about 4 chains.
Measuring might also be marginally useful on my one remaining large-wheel bike that can't be fitted with a Chainglider, but this has a roller brake on the rear, which eliminates the muck and water sprayed onto the chain by calliper brakes.
Since I used up my stock of part-worn derailleur chains, I haven't (yet) found any noticeable wear on the chains under Chaingliders. I'll probably keep on measuring when I change chains, but I don't think it serves any real purpose other than curiosity.
With hub gears, chains can be run with much more wear than with derailleurs, basically until the rear sprocket and/or chainring gets too worn (or until the chain breaks). At which point I intend to scrap the two chains, flip sprocket and chainring and start again with two new chains.
So even without a Chainglider, hub gear chains lastest significantly longer on my bikes than derailleur chains, despite the fact that I tended to favour my hub gear bikes in bad weather and for off-road use.
Adding the protection of the Chainglider, which keeps a lot of the muck (most?) from getting on the chain, increases chain life even more.
So it is quite possible that I will "wear out" before my "two chains for each hub gear/chainglider bike" do, especially as my cycling is spread out over several different bikes.
The exceptions being my two Bromptons, where I reckon a set of 2 chains should last between 2 and 4 years if I continue my current (fairly low) level of Brompton use. When I was using Bromptons intensively for survey contracts I averaged 1,800 to 2,000 kms (about 4 to 5 weeks) of use for a chain before scrapping it.