If Space Exploration Technologies Corp's (NASDAQ:SPCX) Starship reaches space on Thursday, the headlines will likely call the mission a success.

JPMorgan analyst Seth Seifman thinks investors should wait a little longer.

According to JPMorgan, the real test of Starship Flight 13 won't end when the rocket leaves the launch pad—or even when it returns to Earth.

The bigger question is whether SpaceX is getting closer to flying the same rocket again, and again, and again.

That's the milestone that could ultimately determine whether Starship transforms from an engineering marvel into the economic engine behind SpaceX's long-term growth.