WordNet (r) 3.0 (2006):

staying power
    n 1: enduring strength and energy [syn: stamina, staying
         power, toughness]

Moby Thesaurus II by Grady Ward, 1.0:

96 Moby Thesaurus words for "staying power":
   application, assiduity, assiduousness, bulldog tenacity,
   concentration, constancy, continualness, continuance, continuation,
   continuity, decisiveness, diligence, dogged perseverance,
   doggedness, endurance, energy, engrossment, extension, fidelity,
   force, fortitude, guts, gutsiness, hardiness, heartiness,
   indefatigability, industriousness, industry, insistence,
   insistency, intestinal fortitude, lengthening, loyalty, lustihood,
   lustiness, maintenance, might, mightiness, obstinacy, patience,
   patience of Job, permanence, perpetuation, perseverance,
   persistence, persistency, pertinaciousness, pertinacity, plodding,
   plugging, potency, power, powerfulness, preoccupation, progress,
   progression, prolongation, protraction, pursuance, relentlessness,
   repetition, resolution, robustness, ruggedness, run, sedulity,
   sedulousness, single-mindedness, singleness of purpose, slogging,
   stability, stalwartness, stamina, steadfastness, steadiness,
   stick-to-itiveness, sticking power, stoutness, straight course,
   strength, strength of will, stubbornness, sturdiness,
   sustained action, sustenance, tenaciousness, tenacity,
   tirelessness, toughness, uninterrupted course, unremittingness,
   unswerving attention, vigor, vigorousness, vitality, way