According to John Keegan's The Face of Battle, not only did they lead from the front, receiving wounds was an honorable goal!

Here we approach perhaps as close as we are going to get to the officer's central motivation. It was the receipt of wounds, not the infliction of death, which demonstrated an officer's courage; that demonstration was reinforced by his refusal to leave his post even when wounded, or by his insistence on returning as soon as his wounds had been dressed; and it was a punctiliousness in obeying orders which made wounds or death inevitable that an officer's honour was consummated.

Page 189.

However, one caveat is that while officers led from the front, they were not necessarily fighting from the front. Keegan argues that Napoleonic officers, despite their proximity to violence, considered themselves "directors" of violence rather than "agents". Pg. 188. His work is mainly about the subjective experience of battle (i.e. what it's like to fight them), but one of the minor themes of the book is how the officer class gradually recedes from direct combat over the course of military history. The Napoleonic era is characterized by him as an awkward period where direct combat by leaders is beneath their station (he notes testimony on page 188 that an officer once handed a gun to a subordinate to shoot an enemy rather than doing it himself), yet at the same time we are not quite in the industrial era where senior leadership is sequestered in HQs miles behind the front.

While Napoleonic leadership was demonstrated by willingness of exposure to danger, this bravery consigned was seen in both the French and British at Waterloo:

Mountsteven had seen and admired 'the gallant manner of the French officers' during D'Erlon's attack; Dirom remembered 'the Officers of the leading Divisions in front waving their swords'; Dawnson Kelly described 'the Officers being in advance some yards cheering their men on'.

Page 172.

To answer the next part of your question, there was no limit in rank to when this exposure to danger stopped. Wounds and deaths among senior leadership were not uncommon. General Picton is famous for being killed leading a British counter-attack at Waterloo (not only that, he had been previously wounded at Quatre Bras), while Uxbridge (cavalry officer) suffered a bullet wound to his leg so horrific he had to be left behind but managed to hide the pain to uphold his honor. Pg. 126, 129, and 190. Wellington himself didn't shy away from the battle:

A very large number of British officers and soldiers saw Wellington, often at close hand, heard him speak, or even exchanged words with him.

Indeed, Keegan provides a detailed rundown of the Duke's location throughout the day, noting that he generally went where fighting was hottest.

Lieutenant Drewe of the Inniskillings passed under his balcony in Waterloo village, from which the Duke was watching his troops march up, some time after six o'clock in the morning...ten he was west of Hougoumont...early afternoon he was in the centre...sometimes near 'his tree'...sometimes in the interior of a square. After the repulse of d'Erlon's attack he visited the companies of the 95th Rifles in The Sandpit...Later in the afternoon he was mostly behind the right centre, while it was under assault from the French cavalry. Calvert, a major in the 32nd Regiment, saw the Duke east of the crossroads during the attack on La Haye Sainte...and he was quite close to the farmhouse itself when its defense collapsed. During the final phase, that of the attack of the Imperial Guard, many soldiers recalled seeing him...he at times rode alone or with only a single companion...after the retreat of the Imperial Guard, he rode east along the whole line...in the general advance that which followed, he made his way behind the leading columns to La Belle Alliance, where he and Blucher met, at some time between nine and ten. Soon afterwards he rode back to his headquarters in the village inn at Waterloo, to go to sleep on a mattress on the floor because a staff officer was dying in his bed.

Pg. 131-132.