It is recommended that all edits be completed at the same time. Each consecutive save reduces the quality of the file by a small amount. If multiple saves are performed you may begin to see a reduction in quality. This quality reduction is not noticeable if all edits are completed in one save.
To make multiple edits in one save click the icon in the Media Editor after you've added your first cut time range. This will add another field to enter a second time range. Once all times are set click 'Save' to completed all edits.