Personally, I find it pretty workable in Python with a big codebase (but you have to respect the rules like having a good test suite -- you change the time from compiling to running your test suite -- which you should have anyways)...
I find that the current Python codebase I'm working on (which has 15 years and around 15k modules -- started back in Python 2.4, currently in Python 2.7 and going to 3.5) pretty good to work in -- there's a whole class of refactoring that you do on typed languages to satisfy the compiler that you don't even need to care about in the Python world (I also work on a reasonably big Java source codebase and refactorings are needed much more because of that).
I must say I'm usually happier on the Python realm, although, we do use some patterns for types such as the adapter protocol quite a bit (so, you ask for a type and expect to get it regardless of needing a compiler to tell you it's correct and I remember very few cases of errors related to having a wrong type -- I definitely had much more null pointer exceptions on java than typing errors on Python) and we do have some utilities to specify an interface and check that another class implements all the needed methods (so, you can do light type checking on Python without a full static checking language and I don't really miss a compiler for doing that type checking...).
I do think about things such immutability, etc, but feel like the 'we're all responsible grown ups' stance of Python easier to work with... i.e.: if I prefix something with '_' you should not access it, the compiler doesn't have to scream that it's private and I don't need to clutter my code -- you do need good/responsible developers though (I see that as an advantage).