Even at replacement levels you'll shut down your natural production and risk never being able to naturally produce your own T. Needing to do intramuscular injections for the rest of your entire life is usually not a consolation prize people want to sign up for. Plus, in the U.S., should someone lose their health insurance and not be able to afford exogenous testosterone anymore they'd be in a pretty awful situation.
Also you'll likely end up infertile.