We're only here to provide advice.

You're ultimately in charge of (and responsible for) the choices you make.
That said, most people go into it with the same mentality that you do: they don't notice any immediate effects, so they continue to use frequently. You may be one of the lucky few who can keep this up for a long time without obvious problems, but the majority of people experience side effects within a few months of frequent use (obviously, the more frequent and heavy the use, the quicker and more extreme the negative side effects). MDMA causes real, physiological changes in the brain...yes, some people are more resilient than others and can soldier on for a longer time, but the fact remains that your mood is somewhat influenced by your brain chemistry. It's not just psychological.
We warn people to limit the frequency of their rolling only so that they can know to curb their use while they're ahead, rather than ending up months down the road taking ten pills a night that do next to nothing for them while suffering from a variety of mental and emotional problems.
Back on topic: I think chronic fatigue and weight loss are the most obvious signs of use. Even with drugs like meth, these are the most visible causes...the scabs, etc. typical of heavy meth users are mostly self-inflicted. The idea that drugs make you look different is a myth, along the lines of the old "if you keep making that face it'll stick that way" adage.