Yes; to set the default for days until pending sales are deleted, go to Settings (gear icon) > Defaults > Misc Defaults. You can set the days until pending sales are deleted on line 40, and the days until old pending sales are deleted on line 41. Once a pending sale or old pending sale is deleted, the customer information will be retained, but the attached deal structure will be permanently erased. Keep in mind that you can always delete individual deals manually if needed.

Changes made on this screen are saved automatically. If you have more than one lot, you will need to change these settings for each lot. See this FAQ to learn how to switch your computer location from one lot to another. 

See also "When does a pending deal become 'old pending'?"

From the Deal screen, click “search”. Highlight the deal you want to delete and press “delete”.

When the vehicle on a pending deal is sold to another person, the pending deal will be moved to "Old Pending". You can locate Old Pending deals in the Search Sale popup using the filter on line 8.