Snapshot Reports are intended to be used as a prospecting tool and as such are typically expected to only be generated once during the prospecting phase.
Creating a Snapshot report and Refreshing a Snapshot report are two separate products and both charge a standard fee of $2. However, every subscription tier has a number of 'free' Snapshot reports allocated which can only be used towards creating a new Snapshot report for prospecting purposes.
Although a partner can refresh a Snapshot report, this will incur the $2 charge as this is treated as a separate product from creating a Snapshot report.