I think there is no such Option in LOS yet. GrapheneOS on the other Hand has this Option for years.
If you want to safe at least your signal messages/contacts Molly has a similar function to encrypt after a setted time of not using it.
but the UK has the fewest public holidays in Europe. In Germany we have 9-13 but don't get a day off if a public holiday is on a weekend.
And we have a minimum of 20/24 days of holiday on top
Maybe Jolla with SailfishOS would be the best bet.