Yes, if you increase the retention period from one day to three days, Site Recovery saves the recovery points for an extra two days. The added time will incur storage charges since there will be 12 additional recovery points that need to be saved with increase in retention period from one day to three days. For example, a single recovery point might have delta changes of 10 GB with a per-GB cost of $0.16 per month. Additional charges would be $1.60 × 12 per month.