If you always maintain a high standard you get better and faster at doing it right and it stops making sense to think of doing it differently as a worthwhile tradeoff.
Is it worth spending a bit more time up-front, hoping to prevent refactoring later, or is it better to build a buggy version then improve it?
I like thinking with pen-and-paper diagrams; I don't enjoy the mechanics of code editing. So I lean toward upfront planning.
I think you're right but it's hard to know for sure. Has anyone studied software methodologies for time taken to build $X? That seems like a beast of an experimental design, but I'd love to see.
I think you'd be hard pressed to find a team that lacks this kind of cooperation and maintains consistently high quality, regardless of what some nontechnical project manager says or does.
It's also an individual effort to build the knowledge and skill required to produce quality code, especially when nobody else takes responsibility of the architectural structure of a codebase, as is often the case in my experience.
I think that in order to keep a codebase clean you have to have a person who takes ownership of the code as a whole, has plans for how it should evolve etc. API surfaces as well as lower level implementation details. You either have a head chef or you have too many cooks, there's not a lot of middle ground in my opinion.
To make things more complicated, programmers need practice to become fluent and efficient with any particular best practice. So you need investment in those practices in order for the cost to be acceptable. But some of those things are context dependent. You wouldn’t want to run consumer app development the way you run NASA rover development because in the former case the customer feedback loop is far more important than being completely bug free.
I try to design the code in a modular way. Instead of trying to predict future requirements I just try to keep everything decoupled and clean so I can easily make arbitrary changes in the future. Some times a new requirement might force me to make large changes to existing code, but most often it just means adding some new stuff or replacing something existing that I've already made easy to replace.
For example I almost always make an adapter or similar for third-party dependencies. I will have one class where I interact with the api/client library/whatever, I will avoid taking dependencies on that library anywhere else in my code so if I ever need to change it I'll just update/replace that one class and the rest of my code remains the same.
I've had issues in codebases where someone else doesn't do that - they'll use some third-party library in multiple different components and practically make the data classes of that library part of their own domain and have workarounds for the library's shortcomings all over the place so when we need to replace it or an update contains breaking changes or something like that it's a big deal.
There's a lot of things like this you can do that don't really take much extra time but makes your code a lot simpler to work with in general, makes it a lot easier to change things later etc. It has lots of benefits even if the library never gets breaking changes or needs to be replaced.
Same thing for databases, I'll have a repository that exposes actions like create, update, delete etc and if we ever need to use a different db or whatever it's easy. Just make a new repository implementation, hook it up and you're done. No SQL statements anywhere else, no dependency on ORMs anywhere else, I have one place for that stuff.
When I organize a project this way I find that nearly every future change i need to make is fairly trivial. It's mostly just adding new things and I have a place for everything already so I don't even need to spend energy thinking about where it belongs or whatever - I already made that decision.