There are two aspects to maintenance. One is in maintaining a codebase, which is what you're referring to. This greatly benefits from static typing as you can h

There are two aspects to maintenance. One is in maintaining a codebase, which is what you're referring to. This greatly benefits from static typing as you can have good guarantees about your code before you deploy it. The other aspect of maintenance is in keeping a running system up without any downtime. There are plenty of of use cases where recompiling code and relaunching an application is not a viable solution. You need to be able to patch a running system. Dynamic typing is beneficial here because you need the old running code to be able to call into the new code which it knew nothing about when it was originally compiled.