Gradually settling a space colony

--- In spacesettlers@yahoogroups.com, "rick000brooks"
> Somehow I don't think we'll see nearly all the people moving into a
> space colony all at once.
>
> It is going to take time to build up a space colony, especially if
we
> want to use mainly space resources.

A question from a new guy here(who has realised it's about time to
make a proper debut:);

Is it necessary to fill space habitats to capacity? I am thinking
more of Island 3 designs, which are meant to accommodate a population
of millions(10 million is the most I've heard), would it be practical
to 'get by' with a population of only 1 million? As in, would 1
million(or less) be enough to justify the cost and effort of building
a habitat that size?

I realise that the thinking may be more along the lines of, 'fill it
up and then build another one', but would it be comfortable doing it
that way, in terms of stress on air recycling systems, sewage
management systems, and such?