Once vB3 hacking is allowed here, you can go take a look at my
Hack Tracking Log, for example. It's a fairly big hack, about 3500 lines of code (so far, not yet 100% done), 250 new phrases (I tried to be as efficient and reusable as possible ^_^), half a dozen new files, but only like.. 3 file modifications

(and those three modifications prevent
Countless new file modifications in the future, so they're REALLY very much worth their salt

)