Speaking strictly body composition, I think its entirely possible to workout ONCE a week (using ANY style of training, really) and “maintain” the way you look through the way you eat.
Our mainstream culture figures it like this: People want to eat whatever they want, so they must in turn work themselves to death to “even out the score” or “balance out calories” or whatever. This sort of “works” you can see plenty of cases where people (mostly guys) consume whatever they want, because they’re doing mindless activities such as 2 hours on the elliptical or something such as that.
Some primal/paleo folks see it like this: 80% of your body composition will come from food. If you eat sensibly paleo/primal (therefore sort of low carb) then you need NOT do strenuous physical activity in order to lose weight or maintain current weight. Since we are eating for sustenance and nourishment and we typically tend to not over-eat, we don’t have to run ourselves to the ground to create a calorie deficit and thusly lose weight, or to maintain what we have.
In your case, you could probably get away with not exercising at all provided you kept your food intake similar. I don’t know your history, but you look like a naturally skinny guy in your avatar. I’m going to assume you’re a “hard gainer” but if you were once considerably over-weight then this would trump my theory that your genes play a large part in this.
What you talk about doesn’t work too well in terms of performance, but that’s a different story.
I think you may be crediting your “maintenance workouts” with your body comp staying the same when you should give the nod to your diet instead.