I dont know why I haven't replied to this thread before because I certainly have read through it a few times. I especially recall the lovely pics of JP's clover.
I have 5 hives and 2 nucs in metropolitan Brisbane, our state capital city. I am only about 3 miles from the CBD as the crow flies and all the hives are on a 1/4 acre house block but they use the whole community as their resource. They are about 1/2 mile from heavily wooded park land. I know of at least one additional hive in their foraging area but there could be more. Still, they are always bringing in nectar, so it would always seem to me as has already been pointed out that it depends on your local environment. I have seen queen breeders (2) with hives covering every inch of their property. One actually lived within a mile of the CBD and the other not more than a mile or 2 from me and they had been there for years with no apparent nectar source.