
The status can expire if you stay outside the EU territory for too long; under the rules referenced by the authorities it lapses after six consecutive years of residence outside Germany.
Permanent does not mean unconditional. EU Long-Term Residence is intended for people who genuinely live in the EU, so prolonged absences can cause it to lapse.
The material from the German authorities notes that the status expires where the holder resides outside Germany for six consecutive years. Other shorter absence rules can also apply to permanent titles, so if you plan an extended stay abroad you should confirm the exact limits with the local foreigners authority (Auslaenderbehoerde) before you leave, and keep evidence of your ties to Germany.
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