I don't know about your kids but mine would snack all day long if I let them. I got tired of running to the kitchen every 5 minutes and then having my girls not eat their dinner.
We came up with a snack token system. I had the girls help me make 3 tokens for each of them. I cut out large circles and wrote the word snack on them. I let them decorate their own tokens. We made 2 pockets out of paper to hold them in. Again they each were able to decorate them as they wished. One was the start pocket, and the other was the finished pocket. We taped them on the wall in the kitchen. Each time they asked me for a snack, I would let them take a token from the start pocket and place it in the finished pocket. When the start pocket was empty they could have no more snacks that day.
The first day we did this they thought it was great...until they used their tokens up before lunch. And they realized they could have no more for that day. The second day went a bit better but they still used them all up before dinner. Now they have learned to spread them out so they have 1 snack between breakfast and lunch, the second between lunch and dinner and the 3rd they save for dessert. I love this system, it saves me from running around all day and teaches them to savor what they have.
7 years ago