Later, steroids can allow you to push well beyond your genetic limits. It is important to emphasize this, as extreme physical development cannot be maintained long-term without the repeat administration of anabolic substances. The body will always revert back towards its normal metabolic limits once AAS are removed. In this context, some of the gains will not be permanent.
Steroids do permanently alter the physiology of your muscles by adding more cellular nuclei. With higher nuclei content, each muscle cell can manage its volume more efficiently, which allows more rapid expansion. Even after a long period of complete abstinence from training and AAS, the nuclei remain. This may provide a “muscle memory” effect, allowing you to reach your genetic limit (perhaps a slightly extended limit) faster than if you had never used AAS in the past. So in this regard, there are lasting benefits beyond the temporary increase in muscle size itself.