Peace be upon you. According to Sayyid Sistani and Sayyid Khamenei, it is permissible to say 'Subhanallah' more than three times, even with the intention of specificity and partiality. It is preferable to conclude with an odd number, such as three, five, or seven. It has been reported that Imam Al-Sadiq (peace be upon him) said 'Subhanallah' sixty times during his bowing and prostration.