The other half of the answer is to stop treating week three as failure, because in a Korean kitchen it is not — sour kimchi is its own ingredient with its own uses, and there is a reason those dishes exist.
It is what you want for a kimchi stew, for fried rice, for pancakes, and for anything where it is going to be cooked in fat. Heat and fat round off the sharpness completely, and young kimchi is actually the wrong choice for those — it goes flat and loses what made it good raw.
So the version of your problem I would aim at: make a jar a month as you do, eat the first half raw, and plan the second half as cooking kimchi rather than discovering it as a disappointment. Deliberately keeping some until it is properly sour is a thing people do on purpose.
If you want the raw window to last longer, everything the others said applies. But you are also throwing away the good half of a different ingredient.