There are very few
Middle-earth's Dwarves Live Longer Than Most in Lord of the Rings. Within The Hobbit novel, the average lifespan of a Dwarf is around 350 years old. However, in The Silmarillion, where Tolkien compiled many short stories, it's noted that an average Dwarven lifespan is 250.
As Gandalf said, Treebeard is the "oldest living thing" in Middle-earth. Tom Bombadil, on the other hand, is technically older, but he's also otherworldly. So, even though Bombadil is older, he doesn't exactly count.
Fíli, born in T.A. 2859, was 82 years old at the time. Kíli, born in T.A. 2864, was 77 years old at the time. The age of Bifur, Bofur, Bombur, Dori, Nori and Ori has been left unknown. However, we know that Balin was the eldest of the Dwarves after Thorin and that Fíli and Kíli were the youngest “by some fifty years”.
Fili and Kili are not half-elf. They are the maternal nephews of Thorin Oakenshield, the dwarf, and are themselves dwarves of the line of Durin, the Longbeards.
Thorin I (Third Age 2035 – 2289, died aged 254) was the King of Durin's Folk for 99 years, succeeding his father, Thráin I, on his death in T.A. 2190. Thorin was the heir of Durin the Deathless being the great-grandson of Durin VI.
For more than five millennia, the Balrog remained in its deep hiding place at the roots of Caradhras, one of the Mountains of Moria, until in the Third Age, the mithril-miners of the Dwarf-kingdom of Khazad-dûm disturbed it.
Balin: Born 2763, making him 7 years old when Smaug attacked, and 178 when the quest began. In the movie he's depicted as the oldest of the dwarves in the company, and certainly older than Thorin. Dwalin: Born 2772, making him 169 years old during the quest.
Jackson explained that this was because he and his co-writers felt that the character does little to advance the story, and including him would make the film unnecessarily long. Christopher Lee concurred, stating the scenes were left out to make time for showing Saruman's capture of Gandalf.
His exact race is not known, and he remains mysterious—although with some apparent magical and spiritual abilities. Tom Bombadil lived with his wife, Goldberry, just east of the Shire in the Old Forest. He has a few titles, like The First and Eldest.
The Ents appear in The Lord of the Rings as ancient shepherds of the forest and allies of the free peoples of Middle-earth during the War of the Ring. The Ent who figures most prominently in the book is Treebeard, who is called the oldest creature in Middle-earth (a description also given to Tom Bombadil).
Gandalf's age is impossible to determine, but he's likely existed for at least 10,000 years, making him much older than Legolas.
Though Gimli has no children, he is not the last Dwarf of Middle-earth. After the fall of Sauron, his people continued to thrive in the Lonely Mountain. Gimli made his home in Rohan, in the Glittering Caves of Aglarond, and many of his kinsfolk came with him.
He died at the age of 210, after 122 years as king. The graves of the hobbits Merry and Pippin (who had died in Gondor 58 years earlier) were set beside his. He was succeeded on the throne by his son, Eldarion.
By my understanding, the Balrogs were seen as undefeatable up until the battle of Gondolin, when up to eight were slain (3 (?) by the House of the Hammer, 4 by Ecthelion & 1 by Glorfindel), depending on the account read. Gandalf obviously also kills Durin's bane in Moria during LOTR, bringing the total up to 9 (?).
For more than five millennia, the Balrog hibernated in his deep hiding place at the roots of the mountains in Khazad-dûm. He remained undisturbed throughout the Second Age and most of the Third, before the mithril-miners of dwarf-King Durin VI awoke him in T.A. 1980.
In the fictional history, Khazad-dûm was Moria's original name, given by the Dwarves in their own language, Khuzdul. It is rendered (in "translated Westron") as the Dwarrowdelf, an archaic form of what would be the Dwarves' delving in more modern English. Tolkien rhymes dûm with "tomb".
After the death of Thorin in the Battle of Five Armies, Dain becomes King under the Mountain. He redeems the Arkenstone from Bard with a fourteenth of the treasure, which is used to re-establish Dale. Over the next three years, Bard rebuilds the city of Dale and becomes its ruler.
They all united against the common enemy, and so was fought the Battle of Five Armies in the valley of Dale. Thorin was killed in the battle, as were his sister-sons Kíli and Fíli. As his "rightful heir," Dáin succeeded Thorin as King under the Mountain, and King of all of Durin's folk.
Balin was only 7 years old when Smaug the dragon invaded the Lonely Mountain. As a result, Balin was forced to leave his home with his family. Balin's father fought in the War of the Dwarves and Orcs, where he died. Balin was present during this war but the role he played is unknown.
The oldest-living recorded hobbit (except Gollum and Bilbo Baggins, whose lives were extended by the power of The One Ring) was The Old Took, who reached the age of 130. By nature they were of gentle disposition, neither cruel nor vindictive.
In the book, Bolg was crushed and killed by Beorn (in bear form), but in the film trilogy, he is stabbed and killed by Legolas.