When one thinks "sustainable," it's usually around the idea of green, eco-friendly actions and methods. While I fully support that path, that is not what I mean when I say "sustainable." I mean it in the most basic, unloaded version possible: something that can be sustained.
When we're looking at our lives, we can categorize actions in our lives as either sustainable or not sustainable. This seems obvious but the reasoning becomes clear: it forces us to look ahead and see the future not as an extrapolation from the present, but as something that will change over time. This action, or this thing, or these ideas: how long can they last me? Can I sustain this thing? What factors will manipulate my future in terms of this?
Actions: Is the action held back by gear, and will I be limited by that gear? Will I be limited by any other factors? Am I creating things that I can do stuff with, or that will be a burden? Will this be something I want to do for the rest of my life?
Things: Will it last me as long as I need it to? Can I fix it? Can I change it? Can I get rid of it, and can I do so easily? Does it cost lots of money, once or to maintain?
When I'm ranking my various levels of engagement for a specific thing or action, I'm usually judging it based on this framework. I like and respect the idea of being able to have something in my life for many years, and the prediction of that is a powerful tool to know what is truly worth your time.
Examples: certain pieces of technology will last longer than others. In addition, some activities with this technology is dependent on the tech entirely. For those two, enter console gaming. I would rank that as less sustainable than a lot of other actions, because it requires money to maintain, and cannot work without a piece of hardware (whose reliability across the industry has been going down as of late).