One sector holds just one home base. Isn't it then logical to spread as fast as possible and plant home bases in each and every adjoining sector?
However building too many homebases can spread your Power Capacity too thin! Balance between expansion and building is vital. Furthermore you must be sure to adequately protect the sectors you conquer.
There are things you can do to strengthen your presence and defence in your home sectors - use sector bridges to seal off your boundaries, build walls to protect the core of your civilization - there's so much you can do and so many gameplay variations!