I recently went through this process for the Python portions of our large central codebase. It took a few months but most of that was due to coordinating delivery and careful backwards-compatible rollout to multiple streams and licensees, guiding licensees through upgrading their own scripts, etc. Maintaining backwards compatibility wasn't as painful as I expected, but I'm happy that we got to deprecate P2 support on schedule - constantly testing both for every change review gets a little tedious!