Age difference between me and wife?

hi i m vijay . I m living in malaysia now a days far away from wife for few months. I m 10 years older than her. I am 30 year old and she is 20. I want to enjoy for with her for ever and want her to be my wife till my death. As i hear that when men reach to 40 years their drive n libido start decress and when women reach to 35 their at peak that time.so when i will be 45 my will b decrease thn or not and her age at that time will b 35 and she will be at her peak of . And i want to satisfy her then.so what should i do from now. That in later age i become more y n my libido n sex drive dont decrease after 40...please guys dont say that use viagra etc or herbal..i want some natural way