If you’ve had your Magento site up and running for a while, or have been doing extensive testing, you may have noticed that the sales_flat_quote files are growing in size. Log cleaning doesn’t appear to clean up old quotes.
There’s a solution available for download at Aoe Quote Cleaner
Once you download the files, ftp the app directory to your site and then go into admin -> system -> cache management -> checkmark the configuration and then refresh.
Once that’s completed, go into admin -> system -> configuration -> system and you should see a section ‘Quote Cleaning’. Review the schedule and settings and adjust if needed.
Based on your settings, you should see a dramatic reduction in the sales_quote tables and probably improved response time as well.
Many thanks to Fabrizio Branca who authored a great tool to manage your Magento site!