Adjust polling rate.

www/main.js

@@ -415,10 +415,8 @@ function populateRecentBlocks(blocks) {
 }
 
 function getPollDelayAtHeight(height) {
-    let blocksUntilHalving = HALVING_PERIOD - (height % HALVING_PERIOD);
-    if (blocksUntilHalving <= 1) {
-        return 1000;
-    } else if (blocksUntilHalving == 2) {
+    let blocksUntilHalving = calcNextHalvingHeight() - height;
+    if (blocksUntilHalving <= 2) {
         return 2500;
     } else {
         return 10000;