Most of the time spent when loading snapshots is for the analysis of the raw data, the removal of unreferenced objects and the retained size calculation. JProfiler stores the result of this analysis next to the snapshot if possible. This means that opening a snapshot that has already been analyzed is orders of magnitudes faster if a saved heap dump analysis can be found.
If the heap dump analysis takes up a too much disk space, you can switch off the heap dump analysis saving altogether on this tab. The analysis will then be created each time you open the snapshot. In general, if a heap dump analysis is missing or incorrect (e.g. from a different snapshot) it will simply be recreated.