If you decide to go a different route and hand install an older Flash player that doesn't have the built-in time bomb, it appears the version you want is 32.0.0.371 or older.
Unfortunately, there's a free-after-use vulnerability. https://helpx.adobe.com/security/products/flash-player/apsb2...
I'm somewhat surprised nobody has packaged up an old version and wrapped it with "only run flash for these urls" and "don't update the ppapi plugin" type functionality. All the pieces seem to be available: https://support.google.com/chrome/a/answer/7084871?hl=en