I did 3 months in 2014 (I think?) then got stuck. It wasn't so much finding the time that was the issue for me, but deciding on a game I'd like to build. Although that's pretty much the story of my side projects, I spend more time procastinating over what to build rather than
building it.
I keep getting distracted by turning parts of my side projects into their own side projects.
The game I was working on (basic Berzerk clone) was simple enough, but once I decided I needed to use Lua (why? I don't know, I just did) and rewrite the ECS (it's still terrible) and have a vector-based camera for 2D scrolling, which Berzerk never even had (and rewrite the vector class, of course, even though it already worked) and I spent a week writing a state machine for basic enemy AI, implementing it, wondering if an ad-hoc possibly Turing complete pseudolanguage implemented in std::vector was really the correct solution, hating it even though it worked despite being an affront to programming, and deleting it, along with all of the game states that used it, and starting over from scratch, I realized I wasn't actually making a game anymore, so I gave up.
And by "gave up" I mean I'm working on the nth complete rewrite right now. The ironic thing is, it could have been done by the deadline - most of the gameplay was already there, if I'd just focused on the forest and not the trees.
But in my defense, the camera is pretty darn smooth, and I seem to have gotten a lot of useful code out of the effort, but not an actual game yet.