[Spexxvet]

Here's my quick breakdown of required plot points and length in minutes

Party 30
Trollshalls 20
Rivendell 10
Over/through mountains 20
Riddle game 40
Down mountain/eagle rescue 5
Beorn 10
Mirkwood travel 10
Spiders 10
Capture/captive of elves 15
Down river/laketown 15
Lonely mountain/Smaug 30
Battle of 5 armies 30
Trip home 5
Balin visit 5
total 255

That's 4.25 hours of movie. Even two 3 hour movies would probably be enough.

JRR was not as detailed in The Hobbit as he was in LOTR. For instance, here is the entire trip from The Shire to Trollshalls

They had not been riding very long when up came Gandalf very
splendid on a white horse. He had brought a lot of pocket-handkerchiefs,
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and Bilbo’s pipe and tobacco. So after that the party went along very
merrily, and they told stories or sang songs as they rode forward all day,
except of course when they stopped for meals. These didn’t come quite
as often as Bilbo would have liked them, but still he began to feel that
adventures were not so bad after all. At first they had passed through
hobbit-lands, a wild respectable country inhabited by decent folk, with
good roads, an inn or two, and now and then a dwarf or a farmer ambling
by on business. Then they came to lands where people spoke strangely,
and sang songs Bilbo had never heard before. Now they had gone on far
into the Lone-lands, where there were no people left, no inns, and the
roads grew steadily worse. Not far ahead were dreary hills, rising higher
and higher, dark with trees. On some of them were old castles with an evil
look, as if they had been built by wicked people. Everything seemed gloomy,
for the weather that day had taken a nasty turn. Mostly it had been as
good as May can be, even in merry tales, but now it was cold and wet. In
the Lone-lands they had to camp when they could, but at least it had
been dry. “To think it will soon be June,” grumbled Bilbo as he splashed
along behind the others in a very muddy track. It was after tea-time; it
was pouring with rain, and had been all day; his hood was dripping into
his eyes, his cloak was full of water; the pony was tired and stumbled on
stones; the others were too grumpy to talk. “And I’m sure the rain has got
into the dry clothes and into the food-bags,” thought Bilbo. “Bother burgling
and everything to do with it! I wish I was at home in my nice hole by the
fire, with the kettle just beginning to sing!” It was not the last time that he
wished that!
Still the dwarves jogged on, never turning round or taking any
notice of the hobbit. Somewhere behind the grey clouds the sun must
have gone down, for it began to get dark. Wind got up, and the willows
along the river-bank bent and sighed. I don’t know what river it was, a
rushing red one, swollen with the rains of the last few days, that came
down from the hills and mountains in front of them. Soon it was nearly
dark. The winds broke up the grey clouds, and a waning moon appeared
above the hills between the flying rags. Then they stopped, and Thorin
muttered something about supper, “and where shall we get a dry patch to
sleep on?” Not until then did they notice that Gandalf was missing. So far
he had come all the way with them, never saying if he was in the adventure
or merely keeping them company for a while. He had eaten most, talked
most, and laughed most. But now he simply was not there at all!
“Just when a wizard would have been most useful, too,” groaned
Dori and Nori (who shared the hobbit’s views about regular meals, plenty
and often). They decided in the end that they would have to camp where
they were. So far they had not camped before on this journey, and though
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they knew that they soon would have to camp regularly, when they were
among the Misty Mountains and far from the lands of respectable people,
it seemed a bad wet evening to begin, on. They moved to a clump of
trees, and though it was drier under them, the wind shook the rain off the
leaves, and the drip, drip, was most annoying. Also the mischief seemed
to have got into the fire. Dwarves can make a fire almost anywhere out of
almost anything, wind or no wind; but they could not do it that night, not
even Oin and Gloin, who were specially good at it.
Then one of the ponies took fright at nothing and bolted. He got
into the river before they could catch him; and before they could get him
out again, Fili and Kili were nearly drowned, and all the baggage that he
carried was washed away off him. Of course it was mostly food, and there
was mighty little left for supper, and less for breakfast. There they all sat
glum and wet and muttering, while Oin and Gloin went on trying to light
the fire, and quarrelling about it. Bilbo was sadly reflecting that adventures
are not all pony-rides in May-sunshine, when Balin, who was always their
look-out man, said: “There’s a light over there!” There was a hill some
way off with trees on it, pretty thick in parts. Out of the dark mass of the
trees they could now see a light shining, a reddish comfortable-looking
light, as it might be a fire or torches twinkling.