At 65, I Woo Women to Become an immortal

In this world, cultivation runs in stages, and yin gathered from a woman can be turned into cultivation. Ethan Warren has been stuck at Qi Refinement for decades. He is 65, his body is failing, and he has three days left. A system attaches itself to him and offers the one method that will work in three days: dual cultivation. Ethan already has three wives. He also finds the three Lawson sisters injured and treats them. He takes what he knows of modern methods, mixes it with pills far stronger than anything he had before, and goes up into the mountains to try it. His cultivation begins to climb.