The verb prolong has 2 senses (first 1 from tagged texts)
1. (4) prolong, protract, extend, draw out -- (lengthen in time; cause to be or last longer; "We prolonged our stay"; "She extended her visit by another day"; "The meeting was drawn out until midnight")
2. prolong, sustain, keep up -- (lengthen or extend in duration or space; "We sustained the diplomatic negotiations as long as possible"; "prolong the treatment of the patient"; "keep up the good work")