Johnny Ringo said:
There's really nothing in the movie to indicate a great passage of time. Maybe they should have done a token 80's training montage?
Funny you should mention the token montage:
From the 4th draft of the script:
306X. EXT BOG CLEARING - SWAMP - DUSK - DAGOBAH
(formerly part 310)
Luke runs through the dense jungle on the last leg of what must have been quite a marathon. Yoda rides in a pouch on Luke's back. The young apprentice is sweaty and exhausted. He stumbles into the clearing where Artoo has been patiently waiting. As Luke is about to collapse, Yoda throws a small metal bar in front of him. Luke ignites his laser sword and swings at it. He missed and the bar falls to the ground. Luke does too.
LUKE
(breathless)
I can't... Too tired.
YODA
It would be in seven pieces, were you a Jedi.
LUKE
(gasping)
I thought I was in good shape.
YODA
Yes, but by what standard, ask I? Forget your old measures. Unlearn, heh, unlearn.
307X. EXT YODA'S BOG (MONTAGE) - DAY - DAGOBAH
(formerly 308)
At the edge of a wide pond, Yoda sits on a log. In his mouth is a Gimer Stick, a short twig with three little branches at the far end. Luke is nowhere in sight, but now we begin to hear the sound of someone crashing through the foliage. Suddenly Luke appears on the far side of the pond at a run and leaps out toward Yoda. It's an extraordinary leap, but he falls short by six feet, creating a huge splash, which drenches Yoda and his Gimer Stick.
308X. EXT YODA'S BOG (MONTAGE) - DAY - DAGOBAH
(formerly 307)
In the bog clearing, Yoda and Luke sit facing two bowling ball-size rocks. Artoo observes from the side. Luke stares at the rocks, Yoda stares at Luke. Slowly, one of the rocks lifts from the ground and floats up to rest on the other. Luke smiles with satisfaction and turns to Yoda for approval. The floating rock tumbles off. Artoo beeps his review.
309X. EXT YODA'S BOG (MONTAGE) - DAY - DAGOBAH
(formerly 309 and part 310)
Luke's face is upside-down and showing enormous strain. Soon we see why. He is standing on his hands and Yoda is perched up on Luke's feet. Yoda taps Luke's leg. Luke focusing and quickly removes one hand. His body wavers, but he maintains his balance.
Artoo races up to his master whistling and beeping like mad. Luke is trying to maintain his balance, desperately and finally collapses. Yoda jumps clear.
These ideas are carried over from the novel. There is evidence that most of this (like Luke cutting the metal bar) was filmed, but cut out later.