It just depends on how you level up. I do a lot of PvP, so I out level the planets I am on. I am lvl 31 and am still on Tatooine, haven't even started Alderaan. I could skip a planet if I wanted if it were not an essential story planet, like Alderaan.. But then again, that also depends on how you play.. If you are just questing, or not doing many FP's or WZ's then yea, it really isn't a choice...