I was emailing with a subscriber recently and they mentioned how the recent dockworker's strike could make getting inventory difficult. They decided to start holding more inventory on hand in case importing got too slow. Luckily, that strike was short-lived (at least until January) but that points out why looking ahead is important.
If you depend on products or supplies from a vendor and they stop coming, how do you cope? Maybe you have a backup or alternative you can use. Or maybe you just run out of inventory and have to take the hit to sales.
One thing hopefully everyone learned is that the less buffer you have, the more you have to look forward to potential problems. Hold a month of inventory and you have time to find options or wait out a problem. Only hold ten days of inventory, you better make sure you're really good on predicting future problems.
Knowing which products are popular can help too. You'll want to combine your best seller lists from Shopify with Product Reorders to see which products are often bought by new and repeat customers.
Eric Davis
Customer behavior analysis for better Shopify store performance
The Shopify App that increases repeat customer purchases through customer behavior analysis.