code: function doTidyUp(l) {
      var d = parseInt(Date.now()/1000);
      for (var m in markers) {
          if ((l && (l == markers[m].lay)) || typeof markers[m].ts != "undefined") {
              if ((l && (l == markers[m].lay)) || (markers[m].hasOwnProperty("ts") && (Number(markers[m].ts) < d) && (markers[m].lay !== "_drawing"))) {
                  //console.log("STALE :",m);
                  layers[markers[m].lay].removeLayer(markers[m]);
                  if (typeof polygons[m] != "undefined") {
                      layers[markers[m].lay].removeLayer(polygons[m]);
                      delete polygons[m];
                  }
                  if (typeof polygons[m+"_"] != "undefined") {
                      layers[polygons[m+"_"].lay].removeLayer(polygons[m+"_"]);
                      delete polygons[m+"_"];
                  }
                  delete markers[m];
              }
          }
      }
      if (l) {
          if (layers[l]) { map.removeLayer(layers[l]); layercontrol.removeLayer(layers[l]); delete layers[l]; }
          if (overlays[l]) { map.removeLayer(overlays[l]); layercontrol.removeLayer(overlays[l]); delete overlays[l]; }
      }
  }
docs: Remove old markers