If you use juice and HCG you'll desensitize the fuck out of the leydig receptors and REALLY have a hard time recovering. Do a couple bouts of HCG and cruise on low dose test while you do. If you can, come off completely and do a quick recovery period a few times a year.
Do NOT stay on all year-round. We know a guy at the gym who sauced for over 20 years, came off and recovered just fine. He's training clean. Seriously clean, not under-500mgs-of-test-clean, and looks huge and fantastic for such an old fucker. I'm sure if he fucked around and overdosed on HCG he'd be a shriveled old fuck who couldn't get his cock hard if his life depended on it.