How long does the earthworks last? Do I need to come back to the field and redo the earthworks?
You can still use the original machine control file if you wish. However, farmers often re-survey and recalculate the earthworks and create a new machine control file.
The re-survey can also be used for the drainage analysis to check if the re-trim is required.
A new feature we'll have in OSDv2.6+ where you can exaggerate the cut and fill areas using Tools > Cut/Fill > Exaggerate Cut/Fill to reduce the problem of settlement and expansion of the fill.
When we redo a field, it is very quick because the earthworks volumes are much smaller as we are only touching it up. After that it should be good for more than 10 yrs.