prolong in WordNet English dictionary

1. 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"
   prolong  protract  extend  draw out 
   
2. 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"
   prolong  sustain  keep up