If you plan to retire at some point in the future but have no idea when, this is an example of when you plan to retire someday.
Usage Note: The adverbs someday and sometime express future time indefinitely: We'll succeed someday. Come sometime. Let's meet sometime when your schedule permits. This sense can also be conveyed by some day and some time. The two-word forms are always used when some is an adjective modifying and specifying a more particular day or time: Come some day (not someday) soon. Choose some day (not someday) that is not so busy. See Usage Note at sometime.