Lots of things are "long lived".
Most notably houses. They (here in the USA) have 30 year mortgages, which indicate that somebody thinks that they will last that long (the house I'm in is older than that!). The items that are installed in it (wiring, walls, etc.) have lasted that long, and I expect them to last longer.
Maybe the law should be: If you don't support it then you can't claim it is proprietary and its design is public domain for all to tinker with, including software! That might be a worthwhile ting to do.
Oh, if you DO support it, it must have security updates, or you aren't really supporting it!
Then again I live in a dream world.