My take on chain wear for optimum component life:
1 use the largest practical rear sprocket/front chainring combination for the gearing I want. I believe small sprockets/small chainrings wear quicker and also cause the chain to wear quicker.
2 hub gear or single speed rather than derailleur. With no low hanging derailleur, chain is further from the ground, so less muck. Chain alignment is also generally much better. Also much easier to clean the chain/chainring/sprocket when necessary.
3 chain case. Only one I have found that works on bikes not originally designed for them is the Chainglider, and then only for certain chainring/sprocket combinations and on bikes that don't need a chain tensioner.
4 if no chaincase, a low-hanging front mudflap reduces muck and water spraying off the front wheel onto the chain. Still worthwhile with a Chainglider, as the latter isn't waterproof.
5 if no chaincase, a drum or roller brake on the rear avoids muck spraying off the rear rim brake onto the chain. Coaster brake also works, but I don't like these. Disc brakes probably have the same advantage.
6 for derailleur bikes, scrap chains at 0.75% wear to reduce wear on expensive multiple chainrings/sprockets.
7 for non-Rohloff hub gear bikes with very cheap rear sprockets: When the 1st chain needs cleaning, put a 2nd chain and sprocket on, clean the 1st chain/sprocket, when the 2nd chain/sprocket needs cleaning fit a 3rd chain/sprocket , ditto for a 4th. Then start again with the 1st chain/sprocket and keep doing this until the realtively expensive chainring is worn out. Variant with a symmetrical rear sprocket is to reverse the sprocket and use with two chains, some chainrings can also be reversed to even out wear. The Sturmey-Archer rear sprockets I use on my Sturmey-Archer and Shimano Nexus equipped bikes cost about 4 euros.
8 for Rohloff hub gear bikes I will probably treat like a derailleur bike and change chains at 0.75% wear and run several in succession. But clean them and keep them to reuse again to finish off the sprocket and chainring, as hub gears seem much more tolerant with worn chains.