Just to reiterate you will need to upgrade your key for the new version you can continue to use the old version forever w/o upgrading is that correct?
Not really sure what you mean by that. But, As long as, that version still work with Windows 10. You don't need to upgrade to V4 and use that key for it.
But, Windows keep upgrading, changing and so call evolving to something else. There will always be possibility that current version will not work in the future. Than you will need to upgrade to the newer version i.e Fences V4, with new keys for it. To make compatible with Windows on that era. The old V3 keys will not work for the V4 Program
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