Recording warranty information for purchased products

I have created custom entity record to record warranty information such as
Date of purchase
Product code
Product name
Comment
Store purchased from

These fields are currently showing up in a Custom Tab "Warranty" within the Customer record. It was working fine but I need to allow addition of new warranty information as customers start to buy multiple products and send in separate warranty cards.

I am thinking of

1. Creating more custom fields to store these additional warranty
Date of purchase2
Product code2
Product name2
Comment2
Store purchased from2

or is there anyone way to duplicate the fields without creating multiple custom fields.