Part of it is really getting the right sequence of actions to take. Clearly concept/design is the starting point, it directs me to "programming logic" (although not the programming itself, just yet; but more a rough outline of it). From there, I go to my current step, art direction/visuals and audio - which can be freakin' ENORMOUSLY time-consuming; and then finally into the programming and development... and troubleshooting... and testing... and inevitably fair amount of "feature creep."
Sounds like a good approach to me. Personally, I'd prefer not to sequence everything linearly, but to try and have a couple of core tasks running simultaneously. For example, doing animation and game programming during the same period. That way you're less likely to run into bottlenecks, and can keep your mind active more easily.
I got to a point where I had loads of code ready, but couldn't really advance with the programming until I'd designed and drawn the banker characters. I don't think it added to the time taken to make the game, as it was work I needed to do anyway, but it was frustrating and energy-consuming - if I wasn't feeling artistic I couldn't switch to programming to freshen up. I just had to plug away for a few weeks drawing nothing but bankers!
On the other hand, a certain amount of sequencing is good. Bunching up all your tasks together, so that even small tasks stretch on forever, is equally draining! I guess there's a balance to be found that's different for everyone.
Regarding feature-creep, watch out
I thought I was being careful to avoid it, but I got sucked into it without realising! There's features that creep in because you think they'd just look cool or be fun to code, and those are the easy ones to catch. I found myself adding/planning unnecessary features because I was terrified the game would be confusing or uninteresting without them, which is a little harder to avoid
Test on players and judge whether creeping feature ideas are really
necessary, and remember that there's no such thing as a feature which "just takes an hour" to implement!
I'm aiming for a ~2 year dev-cycle on my project, tbh, and progressing right in tune with that. But admittedly, I really don't want to wait that long to have my finished project! XD I wanna be playing it already!
Haha, I know the feeling! I was reluctant to do anything that would take more than a few months as my first commercial product, as I knew I was effectively testing the water. I'm a fan of concise arcadey games anyway, so I didn't see it as a limitation - just a guiding factor on which of my designs I chose to develop fully. I think once I know the market better I'll be more confident about doing a longer project. Good to hear your development is progressing on-target!