I've actually run a campaign that lasted until the PCs were divine rank 5. Longish explanation follows:
When I started making my homebrew (just after 3.0 came out), I still hadn't got around to making the pantheon when my first campaign in that world started so we just used the ones from the PHB. I always meant to make my own pantheon, but never got aorund to it. There was always an ongoing campaign (or two), and I didn't want to change the pantheon in mid-campaign.
As campaigns ended and new ones started, the players grerw to like the consistency of always playing in the same homebrew world. They enjoyed exploring new locations in the same setting and re-visiting places were former PCs had set their mark upon the world. I felt that suddenly introducing a new pantheon to setting that was so well-established with the players would not be a popular desicion, but I still wanted to make my own deities. Tricky. :\
The solution came to me when we first had a campaign go all the way into epic levels. We came to a point were I was starting to run out of ideas for the campaign (around ECL 28 somewhere). There would be a war between the gods, all evil deities uniting against the good deities. Even the bloodwar was to be put on hold, so that demons and devils could fight side by side against the forces of good.
The PCs was destined to become the centrepoint of this war, of course. They, and some of their NPC allies and enemies, became the start of a new pantheon that would eventually repace the old.
As I said, the campaign went on until the PCs had divine rank 5. At that point their ECL was roughly 33, not counting deific status. The amount of preparations required to set up a battle between the armies of multiple deities was exhausting, and planning combats between the deities themselves was even worse. Fortunately I had a job that included
a lot of waiting around doing nothing, so I could use that time to make my preparations. It was an enormous load of work, but it gave something fun to do while waiting.
The campaign was an absolute hoot, and now new PCs get to have former PCs as their patron deities. The players love it!
I suffered from severe DM burn-out when the campaign was over though, and starting a new campaign was difficult.
What campaigns I've run after that one has ended before it went into epic levels, so their hasn't been any more PC deities. It is definitely a possibility though, and I think maybe an NPC from my last campaign has the potential to become a new goblin deity.
The last few months I've insisted on somebody else DMing, so I can finally get around to completeing Vikings D20!