And in the end, the Miami Heat moved one win from yet another Eastern Conference title.
James had 32 points and 10 rebounds, Bosh added 25 points - nearly matching his output from the first three games of the series combined - and the Heat grabbed control of the East finals by topping the Indiana Pacers 102-90 in Game 4 for a 3-1 lead.
Dwyane Wade added 15 points and Miami never trailed, leading by 23 at one point.
''We try to get better every single day, every single game,'' James said. ''When you do that and go out and play the type of game that you are capable of playing, you can be satisfied with the results. And that's what we've built over the years.''
Only the Celtics and Lakers franchises have been to the NBA Finals in four straight seasons. The Heat now have three chances to join that club, starting with Game 5 at Indiana on Wednesday night.
''We got outplayed by the Heat,'' Pacers coach Frank Vogel said. ''I wasn't disappointed in our fight. I was disappointed in the result.''
Paul George scored 23 points and David West added 20 points and 12 rebounds for the Pacers, who got 15 points from George Hill. But Lance Stephenson - who made news in the days between Games 3 and 4 by suggesting he was in James' head - was held to nine and 7-foot-2 center Roy Hibbert was scoreless in 22 minutes for Indiana.
''I was trying to get into his head,'' Stephenson said, referring to James. ''I guess he stepped up and got the win. I can take the heat.''
The heat, maybe.
The Heat, maybe not.
Miami has won the last three games in the series, and going back to the point in Game 3 when the Heat trailed by 15, they have outscored the Pacers by 39 points in a span of about 6 1/2 quarters.
The Pacers won two elimination games in the first round against Atlanta, and need to win three more if their yearlong plan of topping Miami as kings of the East is going to become reality.
The odds are obviously stacked against them. When holding a 3-1 lead, Miami is 8-0 in Game 5s over the past four postseasons.
''We have a chance to play an NBA game on our home floor,'' West said. ''We are going to try to do something that's very tough.''
Bosh scored the game's first eight points, making a pair of 3-pointers and ending a series-long funk. He had scored exactly nine points in each of the first three games of these East finals and was held under 10 points in each of his last seven playoff games against Indiana.
But he came out flying, and probably not coincidentally, the Heat finally had a good start.
''I told him he was going to have a great game,'' James said. ''We got off to a fast start because of him.''
Miami won the first quarter for the first time in the series, going up 27-19 and helped in part by a late 3-pointer from Shane Battier - with replays showing Vogel moved down the sideline toward the Heat forward as he shot from near the Indiana bench.
If nothing else, at least he was trying to beat Big Brother.
Much as he did Sunday, Vogel used the big brother-little brother analogy with his team, trying any way to urge the Pacers to break through against the team that has ended their season in each of the past two years.
''He's got to make a decision at some point in his life, that no matter what, we're not going to lose this fight anymore,'' Vogel said, likening the Pacers to the little brother in that scenario. ''We're at that point.''
The fight isn't over.
But it was awfully one-sided for long stretches of Game 4, and George - who said he thought Indiana outplayed Miami - pointed to free throws as the reason why. Miami was 30 of 34 from the line; Indiana was 11 of 17.
''They won this game at the free-throw line,'' George said.
Miami outscored Indiana 31-20 in the third quarter and kept pulling away before the Pacers used a 15-3 run to make things rather interesting. Stephenson had a layup with 3:20 left that would have gotten Indiana within nine - but it was waved off after he was called for fouling Wade on his way to the basket.
Stephenson scored with 1:31 left to make it 99-90, but James snuffed out any comeback hopes right there with a three-point play.
Miami was without Chris Andersen, inactive because of a bruised left thigh. The Heat also tweaked their starting lineup, with Rashard Lewis in and Udonis Haslem out.
The Pacers were down only 49-44 at halftime - even though Hibbert and Stephenson both had three fouls, the Heat didn't have a turnover until the second quarter, Miami shot 10 more free throws in the half and Bosh and James combined for 32 points in the first 24 minutes.
If there was any doubt, Miami erased it quickly after halftime. James scored five points in a 7-0 spurt to open the second half, and the Heat were on their way.
''They're the best offensive team in the NBA,'' Vogel said.
NOTES: It was the 74th playoff game where James had at least 25 points, five rebounds and five assists, passing Michael Jordan for the most in NBA history. ... George passed Reggie Miller for the highest scoring single-season (including playoffs) by a player in Pacers history. Miller had 2,078 in 1989-90; George entered Game 4 with 2,077 points.