As your codebase gets large, modularity becomes more important - so it might be time you refactor your code with greater size in mind. Another crucial aspect i

As your codebase gets large, modularity becomes more important - so it might be time you refactor your code with greater size in mind. Another crucial aspect is unit tests - as long as you know the project well, you can go in and make a change relatively easily, as long as you know that a system of unit tests will catch any unintended side-effects.