I disagree. If none of your current gains come from drug use, you are natural. Plain and simple. Does it mean you've been natural your whole life, no. Just like if someone made all there gains on gear, then stopped for a few month, I would consider them a juicer. Until, they lost ALL their gains, then gained it all back clean. To me, that's what natural means.
you forget that if you lose all your gains, it's a hell of a lot easier to get them back again. muscle memory, even from juiced gains, will make it pretty easy to get them back. unless you're talking about npc-level size from drug usage, its not going to be muscle that you can't regain after losing pretty quickly.
think about what happens when you diet and your strength goes down. it might take you two or three years to get to using 225 on the incline bench. then you diet and it drops to 185. once you start putting weight on again you're back up to 225 a hell of a lot faster than it took to get there from 185 the first time.
if you do a cycle, blow up to 250, then let it all shrink you back down to 200 pounds, you'll be able to get up to 250 again a lot faster than if you never did that cycle. the only exception is when you use the drugs to get past your natural limit, and that only means when you re-gain the muscle you'll just get to your natural limit a hell of a lot faster than if you never used.
natural means you have never used steroids to aid your gains. because no matter how long you've been off, where you are is a result of the usage. you might be 10 years plus clean, but you ain't natural.