I think I picked this one up while reading Dana Probert and James Wedding’s excellent book, Mastering Civil 3D 2008.
Autodesk AutoCAD Civil 3D uses command defaults to populate all the dialogs that appear when working through your design. It then refers back to these after a command has ended, no matter what changes you had previously applied. This drives me up the wall.
Fortunately there is a switch in the drawing Settings that will allow Civil 3D to keep your last changes as the new default. This setting keeps Civil 3D on the right track by having it remember various settings you set during the course of the day. It is really annoying to adjust a setting, and come back the next day and the default command has returned. This option will stop that from happening.
The Drawing Settings Dialog contains this override. Go to the Settings Tab of the Toolspace, and select Edit Feature Settings from the Drawing header.
The Ambient Settings Tab will reveal the overall settings collection that controls user interaction. Expand the General list, and the settings is about third from the top. Change it to ‘Yes’.