I suggest checking the pricing lists for all the snacks in Epcot...and there are a lot. For example, you wouldn't want to waste a snack credit on a $2 ice cream cone. But a $4.50 Milk Chocolate Pecan Caramel Cluster from Karamel-Kuche in Germany? Good choice!
http://thewdwguru.com/disney-world-resorts/disney-dining-snack-credit-list
On one hand, I wouldn't get something I don't like just because it is more expensive and, therefore, a better use of snack credit. However, if it is $3.50 or less, pay out of pocket if it is something you really want. If it is over $3.50, use the snack credit.
When I did DDP last August, I had my snacks planned weeks in advance.
If you have leftover credits, seriously just go to Germany to the Karamel-Kuche and get what you like and take it home. I returned from my recent trip this Tuesday night and finished my Caramel Chocolate Fudge square yesterday...