or does BUE 'know' not to overwrite data that is part of the same job?
Yes
But any following job that starts more than the OPP later (one hour in your example) will be allowed to overwrite the BKF files, depending on media set specifications and the option to "use overwritable media in target media set before scratch" (tools/Options/Media Mangement)
if you want to keep your data for a week, then set the OPP to 6 days, for two weeks, 13 days etc