Question
How long do I keep the papers about a repair done by a neighbour?
How long do I keep the papers about a repair done by a neighbour depends on what the schedule says and on when it was reported. The conditions document is the text that settles it, and the service desk reads the same text.
In practice: keep the schedule to hand, write down the date, and report it the same week. A report made early is worth more than a report made carefully.