> if you are trying to build cross-platform software (and Windows 2000/XP/98/Vista is cross platform, mind you) you should start building and testing on the various platforms early.

Yeah people tell me they're having problems migrating their Java 8 app to something modern and I can't understand why haven't they always been running all versions of Java in CI, including pre-releases, and just fixing the one thing a month that pops up as a problem. They can still run on Java 8, but they will know it's going to work fine everywhere, and if they find something that won't work in a future version they can engage the Java developers before they release it.