dt1807 Who advised you? Secomba?
Yes, I contacted their support to ask what happens with the lifetime license, i.e. for how long it will be possible to continue to use it.
The response from support was that it will be possible to use Boxcryptor until end 2025 (probably because that is the latest end date of any current commercial subscriptions other than the lifetime license),
There will be a timely notification to let you know when the lifetime license will actually expire. (My guess is that would be around mid summer/fall of 2025)
The support person did not have insight on how Dropbox might/could handle continued use of lifetime licenses within Dropbox and advised to look for alternatives for when the Boxcryptor license will end.