You can read my post about making that trailer on the Campo Santo Blog. After that trailer I also made the Launch Mini-trailers and Accolades Trailer that announced the Xbox One version and Audio Tour mode. Just for fun I also made a Cinematic Playthrough of the game so that my mom could see what I'd been working on.
After I delivered the final version of the Firewatch E3 trailer I had one more thing for them. After the PAX Firewatch panel there was an Idle Thumbs panel where a reader mentioned he thought Firewatch looked like Gone Home, but in a forest. They had a laugh about it, but I thought to myself: "What if Campo Santo and Fullbright were petty, bitter rivals? What kind of trailer would come from that perspective?" (To be clear, the people at both companies are very good friends)
The result was another incredibly goofy video I spent no more than a day working on. Long story short, everyone at Campo Santo loved it, and sent it to Steve Gaynor, co-founder of Fullbright. Later via this connection I got to work on the launch trailer for the console release of Gone Home, which was another dream gig!
Side projects can be a wonderful thing, but it is also still important to have work experience. That is what can separate you from even the most talented editors posting on YouTube. If you're at the beginning of your career, it's important to find work at a post house so that you have the discipline required to work with others, and hit deadlines. If you can't finish a job in a timely manner then it doesn't matter how talented you are.
Multiple times I've had people mention that they were impressed with my side project work, but knowing I had worked at actual production companies is what gave them the confidence to hire me for the job.
In retrospect, what I realize is that side projects can show how passionate a person is about their work. When I think of my friends' side projects, it shows me they don't work just for the money, and that makes me more interested to work with them.
So if you have side projects you want to work on, then do it! Don't necessarily think about job opportunities they'll create while doing it, because that might take the joy out of it. Do what you find enjoyable, and you never know where it might lead!
As a side note, my friend who got the job at The Behemoth also got her job from her side projects. You can read her story on her blog!