Gayatri Sadhna or Gayatri Upasana is the dharma of every dcija (Brahmana). So, after upanayanasanskara, Brahamanas can and should do it every day while maintaining proper hygiene and taking the correct steps. However, it is not meant for everyone. Gayatri Mantra chanting can be done by anyone but the Sadhana has certain rules one needs to follow as it can cause problems if not done so.