what they said, and also...
not only is dxm easy to fall into a habit of using too often, it can have detrimental effects on your life when used in excess. mentally, socially, etc. trust me, i'm still dealing with a dxm habit, and have several close friends that have or used to have destructive dxm habits.
seriously look at your reasons for wanting to take it again: is it out of boredom? are you trying to forget other problems in your life? etc. if so, you're probably better off either not using a substance at all and finding something else to fill your time, or at the very least using something a little more benign, i.e. marijuana. i like eating marijuana rather than smoking for a more "trip" like experience. and contrary to popular belief, so long as your stomach isn't packed full a gram or two at most of good bud is enough for a whole night's high.
i also have some friends and have gone through phases myself where i'll use dxm once, twice, maybe even three times in a week and then not use again for several months. so yeah, its not impossible to use responsibly, its just a tougher craving to resist than many other drugs. just be careful is all i ask brother.
love life.