One should note that the fast-growing newer suburbs and exurbs are much more Republican than the older, more established ones, generally speaking.
Suburbanites like low taxes, fast growth, and "pro-family" policies when they first move in to the young, developing exurbs and suburbs. Once they get more established, they care more about education, infrastructure, etc. and tend to moderate or even become liberal on cultural issues.
Again though what happens to the older suburbs is due to demographic changes, for instance Fairfax and PW in NOVA have seen an influx in minorities in recent years, epseically Hispanics. The same with Montgomery and Prince Georges in MD, the later of which is majority-minority.