In my experience, the viability of a second (or third, or fourth....) base depends heavily on where you are based in the world. Areas with lower labor costs tend to be much easier to operate multiple bases from. Also, if you bases will support multiple widebody flights daily, it makes it easier to absorb the extra labor costs.
In short, it has been said that multiple bases are essentially for your entertainment and should not be relied upon for additional profit. This is generally true, but if you plan well, extra bases can be marginally profitable.