Here's a lesson about receptors in a broad range.
Certain steroid molecules remain active for several weeks, others metabolize into weaker, non-effective steroids after a couple of days in the system. The metabolites of nor-testosterone often stay in the body for up to a year. Eventually all these steroids are excreted in the urine.
Some steroids are much more effective than others at promoting anabolism or growth. Certain athletes also respond to pct better than others.
Not all steroids are created or act the same. Generally, the products which are highest in anabolic properties promote the most growth. Even though it is common to call drugs like anavar, winstrol, and Primobolan highly anabolic, that just means they are much more anabolic, then androgenic. The fact is that drugs like tren, anadrol, d-bol, and test are much more anabolic then the "highly anabolic" items but also highly androgenic.
Some drugs stay in a more receptive state in the blood. That is they remain in the bound or free form which is more likely to be picked up by the receptor site then The bound or inactive form. Drugs like Deca, Anadrol, Dianabol, Cypionate, sustanon, and paraBolan are believed to have a high level of uptake by receptor sites in most users as they remain in the free unbound state at a higher percentage than other items.
Steroids will act differently in each person.some athletes have an extremely high number of receptor sites at the muscle. This allows a great number of steroid molecules to bind and make the signal more dramatic. This may explain why certain lifters can take small dosages of anabolic steroids and grow nonstop. There are other athletes who have a low receptor population at the muscle cell which allows for only a minimal uptake even the most effective steroids. They could take high dosages of multiple steroids and rarely gain any muscle.
If a site is continually hit with the same steroid it suffers down regulation or attenuation which decreases receptor population concentration and sensitivity. When this happens not even mega dosages will be able to deliver the message to the muscle cells.
So there are many factors that affect your cell receptors but in general for every cycle length, I try to take three times the amount of time off. So for example, if you take a two month cycle you would take six months off.