502 is an ok number and the actual number doesn’t matter so much as how you feel. Some guys need to get up over 700 or 800 to feel as well as they want, for other 502 is fine.
Testosterone replacement is just that replacing what the body is not producing and it is meant to be longterm. Watch out for fertility issues if you plan on having kids as T can decrease sperm quality. Clomid or HCG can be used to protect the testicle and sperm quality. It is important not to forget the estrogen as that can increase and needs to be checked. Most men need arimidex to balance the estrogen.