But Harbaugh may have reached the expiration date on the love fest. He's at the point where he must deliver a title before facing the first hints of criticism over his coaching, much as Andy Reid did when the Eagles failed to topple the Patriots in Super Bowl XXXIX.
To get there, Harbaugh must beat his brother, Jim. Much has been made of the "Har-bowl" in the lead-up to Sunday's game. But John's first NFL job was in Philadelphia, and if he wins Sunday, there will surely be some who will wonder what might have been had he coached the Eagles.
"That was never a thought, really," Harbaugh said. "Andy was a guy that I've admired and have learned so much from. I just wanted to do the best I possibly could to make sure that we were successful coaches. We had a great staff, Jim Johnson, all the guys that you know that have been through there."
Harbaugh is the first of Reid's assistants who became head coaches to reach the Super Bowl. He would top his old boss, of course, with a victory over the 49ers. Reid said there would be no jealously if Harbaugh accomplished what he has yet to achieve.
"Not at all," Reid said by telephone from Kansas City.
And if he won?
"I would be fired up," Reid said.
Reid and Harbaugh remain close. They have spoken and texted back and forth over the last few weeks as Reid went from being fired by the Eagles to taking the Chiefs job, and Harbaugh's Ravens swept through the playoffs.
Reid said Harbaugh called to "bounce some things off" of him. He spoke proudly of him just as he said he would if any of his other former assistants - Brad Childress, Steve Spagnuolo, Ron Rivera, and Leslie Frazier - had reached the Super Bowl as head coaches.
"I thought they were all going to be good head coaches, but given the right situation where they could succeed," Reid said. "John's had a great owner [Steve Bisciotti] and a great general manager [Ozzie Newsome]. It doesn't surprise me at all that he has gotten to where he is."
Reid said he never felt any of his coaches were pining for his job. In truth, when all five were there, Reid was entrenched, and the Eagles never considered the possibility of any taking his place.
Letting coaching talent go is just part of the business.
"You have an obligation to help those guys move forward," said former Ravens coach Brian Billick. "I remember Steve Bisciotti was a little frustrated going, 'Look, in the business I came from, when we had a talent like that we'd just start up another division.' Well, that's not the way it works. That's the way I got the job, because of the Dennis Greens, the Bill Walshes of the world. You owe it to your staff to be that same conduit for that opportunity."
While Harbaugh is considered part of Reid's tree, and he gleaned some of his coaching philosophy from him, he said his father, Jack, is his biggest influence. Jack Harbaugh coached for 45 years, most prominently at Western Kentucky from 1989 to 2002.
"He has a great pedigree," Ravens offensive coordinator Jim Caldwell said. "His father is one that was very, very successful and a lot of those things trickled down to John and Jim."
Jack Harbaugh gave his son his first coaching job as a graduate assistant at Western Michigan in 1982. John didn't have a car at the time, so his father drove him to and from work for two years.
"Every morning, we'd wake up and jump in the car and had a half-hour drive to work," Jack Harbaugh said. "We had a chance to talk football and talk about strategy and talk about all the things that a father and son would talk about."
John Harbaugh would eventually become the running backs coach and outside linebackers coach at Western Michigan but moved to special teams when he took a job at Morehead State. He was the special teams coordinator at Cincinnati and Indiana before Eagles coach Ray Rhodes hired him for the same role in 1998.
Rhodes was fired after his first season, but Reid retained Harbaugh. The Eagles' special teams were among the league's best under Harbaugh, but he wanted greater challenges.
"He wanted to be a defensive coordinator and eventually a head coach, and he did not think that remaining a special teams coach would give him that opportunity," Reid said. "You have to remember that special teams coaches weren't becoming head coaches around that time."
Harbaugh's salary by that point was more than what most position coaches make, but the Eagles agreed to make him one of the highest-paid defensive backs coaches in the league in 2007.
He interviewed for the UCLA job and eventually landed the Ravens job when Jason Garrett turned Bisciotti down, but Harbaugh said his experience as a special teams coordinator helped him more as a head coach even if the move to defensive backs coach spurred job offers.
"Special teams is a great place to start as a coach," Harbaugh said. "I had an opportunity to work with every single player on the team. Players are different. Quarterbacks are different than defensive linemen. Defensive backs are different than offensive linemen."
Being the coordinator also allowed him the opportunity to meet with the media on a weekly basis. Reid didn't allow his position coaches to speak with reporters during most of his 14 years with the Eagles, but Harbaugh was able to fine tune his podium presence.
"You get a little work with the media. It was a good training ground with the media, too," Harbaugh said. "That's a pretty important part of this job, too."
And then he smiled for the cameras.
Contact Jeff McLane at firstname.lastname@example.org, or follow on Twitter @Jeff_McLane.