[CydeWeys]

Brake pads aren't on that list? That's the other obvious consumable I can think of.

And for what it's worth my mechanic ran low on chains and sprockets at some point. I don't know if that was just him or larger supply chain issues though.

[mauvehaus]

Brake pads wear out after thousands of miles. Most of the neglected bikes in the US got parked long before they accumulated enough miles to wear out brake pads. I've got maybe 4000 miles of mostly urban commuting (i.e. much harder on brake pads than rides in the country) on my nice road bike and I haven't changed them yet. For casual cyclists, brake pads are a lifetime part.

Possible exception: glazed brake pads, but still relatively uncommon. Cables and housing are much bigger wear items for most bikes. Mostly because they aren't stainless at the low end and rust.

Chains will also rust, but it's pretty hard to end up with an unsalvageable chain unless a bike has been left outside for a long time. Source: left my beater road bike outside at the curb for 9 years in Boston, including winters. Lubed the chain a couple times a year. It still runs.

[midnightclubbed]

Maybe on road bikes but MTB brake pads are definitely a non lifetime part. Replaced my rear pads at the weekend, maybe 0.2mm remaining after around 800 miles or so of riding.

Getting oil on pads is also fairly easy to (accidentally) do. Learnt to be less liberal with the spray oil the hard way!

Unfortunately for bike shops replacing disk brake pads is trivial. Bleeding the Hydraulic system not so much, if it wasn't for the stopping power I'd trade back to brake cables any day.