Don't get me wrong, Ive heard of this type of Freeform Gming before, I even sort of posted about it in another thread entitled "off the cuff" but the notion still stands in the face of my understanding of how RPGs work.
I too have 30 years experience, primarily as GM, and have always kept my players happy. How I avoided the 'railroading' thing however was a mixture of allowing a bit of freedom in the nuances of a adventure without anything truly threatening the core plot and presenting adventures that were interesting enough my players didn't feel like they had to go off on wild tangents.
If my players, for example, were headed to a particular world for a particular purpose I would have their destination detailed fully, and then perhaps some general notes on other settlements, features of interest, NPCs etc. just in case they deviated a bit. But.. if they suddenly decided while in orbit to change their plan and jump out to another planet they had never visited before (and therefore I hadn't detailed) the session would have been over. No way Im going to pull an entire world out of my backside, not and feel confident it would be as well established, colorful and rich as the environments I create when given some time.
Im a pretty creative guy and as said, have quite a bit of experience but with a universe as full and in depth as StarWars each session requires quite a bit of research to make sure your creations are true to cannon and if completely new, fit in with the established genre. Not to mention, there isn't a spot on in the universe already detailed sufficiently to allow a session to be played without at least a little fleshing out by the GM. RPG are just so damned intimate when it comes to interaction between the PCs and the universe around them. Every session is an exercise in creating reality.
You are under the impression that there is only one true way to GM. There isn't. What works for me may not work for you. I can understand why you would want to break in the session because of the players going completely off the rails. However, I believe you are short changing your players who spent time and money to show up because you cut the session short. The thing about locations in Star Wars is that there isn't anything that says a planet has to be X, Y, or Z. It's up to the GM to decide it for planets not even detailed in the canon. Fortunately, that list of canon planets is rather small and you have the leeway to make up planets as you see fit.