Where there is a duty to retain, risk is accumulating in silence
Pick a case to see why it matters, with the specific legal basis.
Notarial deeds
A notary keeps their protocol (the collection of original deeds authorized each year) not for a fixed term, but permanently. Spain's Notarial Regulation mandates that indefinite retention, and the protocol passes to the succeeding notary or to the regional notarial college's General Archive of Protocols when a notary retires.
That means a deed authorized today, signed electronically, has to remain defensible in 50 or 100 years, well beyond the horizon of any current cryptographic algorithm. If a property sale, a will, or the incorporation of a company can no longer be authenticated, everything that depends on that deed (ownership, inheritance, derived contracts) is thrown into doubt.
No manufacturer promises a computer capable of breaking RSA-2048 before 2035. But "permanently" is not a timeframe that calendar can be measured against: it outlasts any estimate, optimistic or conservative, of when that computer will exist.
If your organization fits one of these cases, the first step isn't deciding what to do: it's knowing how much risk has already accumulated. Audit a real document and see for yourself.