I don't think it can be explained by "wearing out of receptors" specifically. But the guys who dump a lot of drugs into their bodies early on just seem to fall apart quicker. You could say they take a fast track to where others are much later on, peak earlier. I don't know, maybe they could be better ultimately if they took it a bit slower.
Higher levels of testosterone in the body is know to:
- upregulate myostatin (which is why gains slow down around week 10-12)
- induce insulin resistance in muscle cells
Insulin resistance in the long term is related to numerous pathologies, including diabetes, heart disease, certain cancers.
There is no evidence that testosterone use 'wears out' androgen receptors (the term for other drugs is that they are up-regulated, meaning there are more).