Exactly @drPhil !
Or if you wish to start tuning, you can maybe change the starting time, to make sure your resources have the least things to do at that time, or even split the schedules to have one data verification for the GDSP1 and another schedule a bit later for GDSP2 when the other is close to complete, to avoid the both running at the same time.
It all depends on your infrastructure and its capacity to process parallel I/Os as this is really read-intensive process.
Regarding the amount of data to process, the more data has been written, the more data would have to be processed. If you don’t perform any backup at all, the incremental data verification will have nothing to do.
So if you expand the time between two DDB verification jobs, then you would have 1) more data to process and also 2) higher probability/risk to have not OK blocks still beeing referenced and not marked as invalid.