Replacing the cassette and chainrings every time you replace the chain is excessive. Chains wear most quickly so have the shortest lifespan. I generally replace

Replacing the cassette and chainrings every time you replace the chain is excessive. Chains wear most quickly so have the shortest lifespan. I generally replace the chain when it’s worn by 1/16th of an inch over 24 links (see https://www.parktool.com/blog/repair-help/when-to-replace-a-chain-on-a-bicycle https://www.parktool.com/blog/repair-help/when-to-replace-a-...), which is around 3000km for me. Cassettes easily last for several chains — you can tell when they need replacing because the teeth look like shark fins. Chainrings last even longer. I’m also not convinced that a worn chain actively wears the cassette and chain more quickly. How would that happen? The loads involved are the same. In my experience putting a new chain on a worn cassette just results in the chain skipping over the teeth when under load. If you notice that it’s easily fixed with a new cassette.