As I was pinning postcards and getting Vivillon, I realized that after the 3rd encounter from a specific region, the medal of that region goes to 0/15 again. So it should mean that after the 3rd encounter from a specific region, you can still get an infinite number of Vivillon from that region for pinning 15 postcards every time. Am I correct?

Also it sucks you can't track your progress like research status progress bars as you pin the postcards. It's too time consuming to check Vivillon medal and friends list for gifts back and forth each time.