few decades;  many decades;  several decades
 without intermission for ten (long) years;  with constancy of purpose for ten (long) years;  in the same old rut for years on end
 without intermission for ten (long) years;  with constancy of purpose for ten (long) years;  in the same old rut for years on end
 Thirty Years' War (1618-1648)
 veteran player;  experienced player;  veteran (at a job)
 the pace of change makes ten years back seem like ancient history
 10 year career in the highest division is enough for anyone
 grudge of ten years' standing;  harbouring a grudge for many years
 life is short; (lit.) life is just fifty years