Legolas is still full of energy after three days of running without sleep

The sun was sinking when at last they drew near to the end of the line of downs. For many hours they had marched without rest. They were going slowly now, and Gimli’s back was bent. Stone-hard are the Dwarves in labour or journey, but this endless chase began to tell on him, as all hope failed in his heart. Aragorn walked behind him, grim and silent, stooping now and again to scan some print or mark upon the ground. Only Legolas still stepped as lightly as ever, his feet hardly seeming to press the grass, leaving no footprints as he passed; but in the waybread of the Elves he found all the sustenance that he needed, and he could sleep, if sleep it could be called by Men, resting his mind in the strange paths of Elvish dreams, even as he walked open-eyed in the light of this world.

‘Let us go up on to this green hill!’ he said. Wearily they followed him, climbing the long slope, until they came out upon the top. It was a round hill smooth and bare, standing by itself, the most northerly of the downs. The sun sank and the shadows of evening fell like a curtain. They were alone in a grey formless world without mark or measure. Only far away north-west there was a deeper darkness against the dying light: the Mountains of Mist and the forest at their feet.

‘Nothing can we see to guide us here,’ said Gimli. ‘Well, now we must halt again and wear the night away. It is growing cold!’

‘The wind is north from the snows,’ said Aragorn.

‘And ere morning it will be in the East,’ said Legolas. ‘But rest, if you must. Yet do not cast all hope away. Tomorrow is unknown. Rede oft is found at the rising of the Sun.’

‘Three suns already have risen on our chase and brought no counsel,’ said Gimli.

The Two Towers, Book Three, Chapter 2: The Riders of Rohan.