For most who use it (myself included), DMT really seems to contain some kind of self-regulating mechanism. I have about as addictive a nature as anyone I know, but this stuff is just so beyond the beyond (and beyond and beyond and beyond), that I'm forced to adopt an uncharacteristic attitude of moderation.
A lot of us first discover this thing and then want to push the limits - and extracting your own means you'll always have an inexhaustible supply if you want it. But for most (and this has been my experience), there's just no way to sustain an aggressive approach for very long. It will let you know in NO SUBTLE WAY when you're starting to cross the line.
Then there's always the very distinct possibility that you'll break through once and be done with it. If you go deep enough, once will give you enough to chew on for a very long time, believe me. DMT is nothing like any other drug you've ever encountered.