Mark loves to prod me about cross-chaining, because it’s formally a naughty-no-no. I thought I’d give some observations, since I am a chronic cross-chainer.
Cross chaining wears the sides of the sprockets, which is never what wears out. I ride like I am a 1×9 unless I’m on hills. No problems. All major makers support 1×11 (single gear in front, all the way back and forth in the rear).
Cross chaining puts a side load on chain pins, so use a chain whose plates don’t pop off. Most are made by KMC, with a brand label on them. I found SRAM branded chains hold up better. SRAM was the first to offer 1×11 drivetrains. KMC branded, Shimano branded, etc would pop a link by 600 miles. Maybe better now, but I have no reason to change brands. Bell chains are just too heavy/slow/frictiony, but work fine. Whippermsn chains are super durable, but expensive. Chains with a dimple or flat pin edge are better than the ones that look like a wite cutter went after them.
Wear on the teeth, ramps, and pins of the cassette/chainrings is due to shifting. Side loads don’t matter much, but heavy loads do. Don’t shift under high load, and they will last longer. If you hear a crunch when shifting because you waited to downshift, that’s more damaging.
Wear on chains is mostly from higher wattage, incorrect lubrication, and grit abrasion. Clean and lube your chain any time you can hear it at all. Try different lubes and see what you like. You can even throw it in a jug of 50wt motor oil, or molten candle wax if you like, but make sure to wipe it off well. Oil only needs to be inside the rollers. Anywhere else attracts grit.
Wattage, well, whatever power you can put into a chain is part of the fun, but if you are 285 pounds like me, and stand to power up a hill, expect more wear.
Lastly, when your chain gets to 0.5% stretched, replace it. Letting it go longer causes additional wear on the sprockets.
The only other issue to bring up is practical, not wear related, and that’s dropped chains.
If you are all the way tiny in the back, and shift up to the big ring in the front, expect to drop the chain off the outside, onto the crank arm.
If you are all the way small in the back, and try to shift to the small ring up front, expect to drop your chain between the cranks and the frame.
If you are fast, you can soft pedal, shift 2-3x in the rear, then shift up front, before losing much momentum. Chain guards and idler arms are not super effective at preventing drops caused by cross chaining.