It's been formally around since the First Intifada in 1987, so getting on for forty years, prior to that Ahmed Yassin had set up Mujama al-Islamiya in 1973, a charity connected to the Muslim Brotherhood (founded in 1928) - so yeah, depends how you define 'long'? I'm throwing the dates out there for context for other readers not because I particularly want to challenge your assertion that Hamas hasn't been around for long. For those looking for a pop reference, Hamas' career has been around as long as Kylie Minogue's career.