Grimy drive trains are sticky and they absorb power. Why waste power when you’ve invested in aero gains?
So before every important event I remove the chain, the mech., and the cassette, and clean them all thoroughly. I clean the chain ring on the bike.
I lubricate the mech on the work bench and then re-fit it ……
….. then re-fit the cassette after cleaning every sprocket individually.
Then I check the clean chain for “sticky links” and if I find any I free them up using a chain tool.
Then I fit the chain with a new “Quick Link” and lubricate it in-situ.
I replace my chains once a year unless they get wet and then I replace the chain for the next event.
I’m not a powerful rider so I don’t stretch chains, but if you do put out a lot of power it’s worth buying a chain wear gauge as a checker.