For the purposes of this particular clause, we need to ensure there's not information floating out there needlessly, but if it's too broad to have “for as long as is necessary”, how do you define it so that the officials and private operators whose information we want to protect is comfortable? What's a reasonable term? I can't think of reasonable language, other than a set date.
Generally, there are a set number of days, months or years that you can retain information, and then it has to be destroyed.