I think you're thinking about it backwards. It's usually not thinking "what could I tweak today" that results in adding something to .vimrc. It's "I keep doing this a lot / this feel uncomfortable, maybe there's an easier way" that results in changes. And if you take time to actually implement it, that's a good indication it was worth the tweak.

Let's say you work with splits a lot. Sure you could press ctrl+w all the time, but it's a bit annoying. Rebinding doesn't take much time, but makes it (in the presented example) actually simpler. So did it waste time? A minute or so. Does it make life easier? A little bit. Did the "coding time" suffer? Who cares about a minute or so ;)