Hummer aggression at feeders

I got a comment on one of my posts about aggressive hummingbirds guarding feeders and keeping other hummers from accessing the nectar. Question was if this is unusual. Answer from my experience is that it's common behavior. I have two feeders out of sight of one another. At one, I've seen six birds feeding at once, a little skittish, but able to finally get a drink. At the other there's a female that guards the feeder all day using a great deal of energy to avoid sharing. The group feeder gets refilled every three days or so, the guarded one can go two plus weeks and still not be empty. What the hummers are doing this time of year is putting on weight for migration, lots of weight, 50+% gain. So the ones with unimpeded access may be getting up to the required energy level faster than the one with control of the feeder at the cost of endless guard duty chasing off interlopers. It would be an interesting experiment to see which gains weight faster. Under conditions of very limited food supplies, guarding might be the best stategy, but unlimited access might make a looser approach better. Maybe a moral here, greed is dumb when the world is rich.