If you spend a lot of time making a selection, and you may want to modify it later, be sure to save it.
The photograph must be saved using the PSD file format.
To save the selection, go to Select > Save Selection, and enter a name for the selection.
You may want to save the selection without feathering.
You can always add feathering, and can change the feather radius, later.
However, if you save the selection with feathering, the feathering is fixed.
When you reopen the file, and you want to use the selection, go to Select > Load Selection.