There's a reasonable point in here, that for some companies, there is no distinction between maintenance and ongoing development. You're just constantly thinkin

There's a reasonable point in here, that for some companies, there is no distinction between maintenance and ongoing development. You're just constantly thinking of new features, and the work of building those features and changing the way existing features work is comingled. In that case, you have no such thing as maintenance. This model is probably more common, thanks to the rise of SaaS, and automatically updating end-user software. But sometimes you sell a product, and the product or some component of it (perhaps some integration with another tool) of it really is in maintenance mode. You decide that acquiring new customers is unlikely, or not worth the cost, and you make the bare minimum of changes necessary to keep the lights on. No one touches it for months, and when they do, there's a bug fix. Perhaps customers have new ideas for using the software, but you're not going to do them. That's maintenance mode. It still exists. It's not a fun place to be, but it's real. It even can be valuable (since fixing the occasional bug report can be very low effort, but necessary to keep customers around).