Prospect versus Customer Database

We’re new to Shopify. What do most Shopify customers do with regard to saving and managing incoming leads? Do you mix them into your Shopify Customer database, or do you keep a separate CRM database just for leads?

If you keep two databases, what do you do when a prospect turns into a customer? Do you remove them from the lead system and move them to the Customer file or do you just mark them as a current customer?

I really hate to keep two databases with overlapping information but the Shopify Customer file does fill the need for prospect tracking and follow up.

Thanks for the help.