Firstly, THANK YOU for making this informative, helpful thread!
I have kept guinea pigs for just over 10 years, and I admit that part of me cringed a little before I clicked on this thread, expecting misinformation and common misconceptions.
But this thread is great! Accurate information and dispelling myths, especially with regards to appropriate cage size (which is something that really pisses me off).
Anyway, I'd better introduce my boys. They currently live with my brother, as we've moved into a rented house and our landlord doesn't allow pets, and our new place isn't big enough to keep guinea pigs indoors in our giant home-made cage.
The Doctor:
The Scientist:
The Captain:
The Professor (recently died, he had always been sickly and was quite old when we got him, finally had to be put to sleep due to a tumour in his throat):
I miss them, but at least I still get to see them a lot when I visit my brother.
smile
And again, to echo what you said in the OP, all 4 boys lived harmoniously together in one cage for more than 2 years, even though they did not live together since infancy and were all introduced to the group at different times and ages.
I am convinced the key was proper introductory periods, and having a big enough cage to get some alone time from each other.