Then I'm interested to know when, what's the number of years, should we drop backwards compatibility for a certain version of interface, if ever. I'm sure there

Then I'm interested to know when, what's the number of years, should we drop backwards compatibility for a certain version of interface, if ever. I'm sure there're still a lot of punch card programs and today no new system support it. Also there's always a option to not use the new technology that dropped backwards compatibility, which is why many people still buy second hand game consoles and casette players. I love them, but I accept the fact that they're no longer backward compatible with new devices.