Some people use it mid cycle to help with testicular atrophy. Some use it PCT. Read Radars Sticky on PCT. It will answer these questions. Also here is some more info I found a while back.
When your body sends out LH (leutinizing hormone), it signals your testicles to begin producing test again. During your cycle, LH release will be suppressed and will remain suppressed for a few weeks after your cycle. HCG mimics LH and helps your testicles start producing testosterone. For our purposes we should view HCG as a “bridge” between your cycle and the time your LH returns to normal function. However, HCG when used to heavily or for too long will actually suppress natural test production so it can be counter productive.
I think people have been using HCG for so long like clomid for PCT. It is different and should be used for what it is intended for. Check out Radars sticky on it. Peace bro.