No, it doesn't return them to their original state. It highly depends on the duration of use and orignal ohms of the cartomizers. e.g. LR will rise while HR will decrease in ohms over time. Generally, a standard sized cartomizer will last for about 10ml. You will have to decide whether cleaning it is worth it or not in the end.
Some sure fire ways of knowing that the cartomizer is coming to the end of it's lifespan. Is that you will notice a drop in performance (less vapor,
throat hit, etc.) and the draw will become tight. The last sign would be if you start tasting a burnt flavor which means it's time to toss it immediately in the garbage.