I am afraid that I do not see how one could ever return to one's original timeline after leaving it (if leaving it is indeed possible.) I shall try to illustrate what I mean.
The time traveler lives along timeline A (black line).
At point X, the time traveler goes back in time to point -X (via upper red line).
At the moment of transfer, timeline A branches off into timeline B (upper gray line) and timeline C (green line). The B timeline is that state of the universe which continues to exist after the departure of the traveler. (It may or may not be the same as timeline A.) The traveler, at point -X, will now move along the C timeline.
At point Y, the traveler goes forward in time to point +Y (via lower red line).
At the moment of transfer, timeline C branches off into timeline D (blue line) and timeline E (lower gray line). The E timeline is the state of the universe which continues to exist after the departure of the traveler. (It may or may not be the same as timeline C.) The traveler, at point +Y, then moves along the D timeline.
Red lines do not indicate timelines, but rather the instantaneous transfers of the traveler from one point to another.
I apologize both for the crudeness of the illustration and my lack of knowledge concerning these things, but it seems to me that if the act of time travel in itself changes the timeline, then our traveler can never return to his origin point.