I can tell you I personally find reading and studying a premade adventure more work than making one. On top of that, they can be kind of railroad-like.
When ran Pathfinder, I would spend HOURS and HOURS prepping. I mean like a 4 hour game would be perhaps 12-16 hours between conception and notes. EotE I spend about 4-6 hours prepping a session... the system is just that easy to prep for me.
Here are a few tips
1) Make 3-4 generic encounters, ones you can put anywhere. Random thugs, law enforcement, Bounty Hunters, etc. These can be pulled out anytime your players want to go off somewhere you have not planned. IMPORTANT: Never let them know! Always seem like things are prepaired this way.
2) Use the Adversaries Statblocks. They are your friend. Need an alien baddie? Grab that Defel Assassin... rename it what you want... GO! Occupationally swap out a Talent or two to keep it interesting.
3) When your characters seem to be completely off track and going completely off from the story, keep your eyes peeled for a way to steer the story back. Do not railroad them by forcing them to go somewhere, just change it to fit what they are doing. If they are supposed to goto the Cantina for an encounter and they goto the Ship Hanger... figure out a way to work the same thing there. IMORTANT: Never let them know.
4) Do not be afraid to come up with interesting mechanics, special rules (a la Mini games). I have done several things to mix things up. I have had a "Social Combat" for example. Use strain and have them battle like combat but with words. Use the Sabbatt rules in the Game Day adventure. I also will make "Environmental Criticals" that players can trigger with Triumphs (your blaster blows off a steam valve and causes these effects) Stuff like that.
5) Listen to the "Order 66 Podcast" and "Happy Jack's RPG Podcast." Order 66 is just awesome because the hosts are great and it is all about EotE. Happy Jack's is almost exclusively about GMing and full of tips. Especially the lastest Season 10 episodes. WARNING: Happy Jacks is for Mature audiences. LOL