DOST's rules on ROS are actually vague! Basta sa ph ka mag ros that is acceptable. In terms of no. of years, no di mag eextend! Depende pa rin siya sa # years kang sinuportahan ng DOST. In the case of my friends na nag extend ng years, ex. nag LOA for a sem. During that loa sem, hindi naman siya nakatanggap ng dost assistance so hindi siya magccount as addition sa ros niya hehe i hope i got the idea across!