Re: How much Sugar per hive, if no nectar.
How are you going to know when an area reaches critical mass?
One feeds when one needs to. Which isn't all year round. Not even most of the year by any means.
It is always a good idea to understand what you are getting into and what you need to do to prepare for the future. But you may be getting ahead of yourself. Even though you did get a good answer of 20lbs of sugar per hive per year.
"It's not what you look at that matters, it's what you see." Henry David Thoreau, Mark B