How aggressive should one be with replacing aged steel pipes in a Norfolk VA brick house?
It depends on the water , steel can last a very long time in some waters, so doing nothing unless there is a problem is an option. Find out from neighbors ( with steel pipe) if there have been problems. If any is accessible , a piece of pipe could be removed and examined  as an indication of the whole system but opening an old pipe connection can easily make problems. Pipe wall thicknesses are measured routinely in industry  with ultrasonics but it would be expensive to hire an inspection company.