the point is they don't continue indefinitely
I would have thought that was rather obvious/clear and taken 'as read'. Otherwise the planet would be overrun with bees! But what with a high first year mortality of swarms, the age of a well founded productive colony might be well in excess of that average figure before some fatal mishap overcame them (a run of poor seasons, a marauding bear, looting hominids, tree falls over, forest fire, lightning strike, etc).
I still think stating a colony lasting (about) 4 years, with varroa, is a very misleading statement.
As Chris says, a colony may be able to survive with the parasite indefinitely (it's demise would be for the other possible reasons) and many have to treat each year or the colony would likely no longer exist the following spring. Perhaps John Harding is spot on with location, location, location.
The OP asked a very non-specific question about wild honey bees, not any one particular strain. Bees are found around the world, not just in someone's back yard.
