Requiring all your constants to be configurable seems like a great way to bypass (potentially critical) code review and QA. I can totally see changing something

Requiring all your constants to be configurable seems like a great way to bypass (potentially critical) code review and QA. I can totally see changing something like "number of months" causing extremely non-obvious issues (e.g. integer overflow in something 20 stack levels away)...once you make it a configurable constant though, changing it won't be QA'd at all.