This is the date at which the key will cease to be usable for performing encryption or signing operations. 6 months is a reasonable time to set it to. You will have to either change the expiration date or generate a new key or subkey after this amount of time passes.
Data honetatik aurrera gakoa ez da erabilgarri izango enkriptazioak egiteko edo operazioak sinatzeko. 6 hilabete zentzuzko epea da horretarako. Iraungitze-data aldatu edo gako berri bat sortu beharko duzu epe hori igaro denean.