Steroids modify gene expression, bone structure, etc.
Once you join the dark side your not a natural.
Natural means NATURAL, you and only you.
PH's, gear, anything, at any time means your not natural.
You can hold steroid size and strength pretty much forever as long as its not too far past your upper limits.
Reaching those limits on your own would take FAR longer.
Hell you can hold far above your limits for a very long period of time as long as you are committed.