I think this is where the part of knowing your body and the way it responds to exogenous hormones. Test only cycles don't really shut me down hard for HCG, but the next guy you ask will tell you different. The use of HCG for me is not warranted unless I am using hard shut down compounds or long cycles with high doses. Which I really don't do either anymore now that I'm older and because I'm not bodybuilding on a professional level. At this point I'm cruising to maintain a healthy, athlectic physique and striving for youthful bliss at 40 basically. I do this mainly with my diet and training and some gear in the mix. Everyone is different though, what works for me won't for the next guy beside you. It's the way we are engineered individually. It's all about your age, your body, and your goals. I have spent many years and trial/error to get to know my body; the good, bad and the ugly for that matter and thats what I base my regimens on. Now for the community I go with the science and research to advise. I wrote a post on HCG and maybe this will help you:
http://www.eroids.com/forum/steroids-qa/anabolic-steroids/hcg-what-is-it...