Yes, it’s pretty much like a plan to eat one potato chip while continuing to hold the bag in the hand.
Though I know many who have done very few cycles, for whatever reason of doing very few. For example, becoming a doctor and just not wishing to have people scrutizing and questioning unusual changes in the physique, getting married and not wanting the wife to view the physique as being a product of steroids (when in fact it IS mostly the product of very hard work and genetics), and other reasons. So it’s not as if it’s too hard to stop if there is good reason to do so.
As for keeping the gains, a lot has to do with whether your usage took you past where your body ever could have gone with natural training. If not, then generally the gains are maintainable (though the extra glycogen and glycogen-associated water, and other extra water if any, will not be maintained.)
Actually it’s possble to maintain somewhat above what could ever have been obtained naturally (granted, that outcome is one that can only be guessed at not measured though if one has been training very well for a very long time there’s a good general idea of it) because at least one permanent and beneficial-to-muscle-mass occurs or can occur from steroid use. Namely, satellite cells can be triggered to fuse with mature muscle cells, thus resulting in those muscle cells gaining nuclei (muscle cells, unlike most cells, have and put to use many nuclei each, not just one.) This permanently increases the protein synthesis capacity of the muscle.
Anyway, there is a lifetime benefit to a really effective cycle. (Not so much so if to any degree, though, with a piddling cycle.)