Show Temperature - Why code Not Stable for extended period of time?

you have competing/overlapping intervals / timeouts...

...give this a shot...

// show numbers from 1 through 109 with red and green flashes:
// a red flash for each tens, and a green for each ones;
// example: flashLEDs(21); // flash red twice and green once
// Note: you cannot call it more often then about every 10 seconds
function flashLEDs(intOrLED, flashesAsStr) {
  if (!flashesAsStr) {
    flashesAsStr = (
        "RRRRRRRRRR".substr(0, Math.floor(intOrLED / 10))
      + "ggggggggg".substr(0, intOrLED % 10) );
    intOrLED = null; }
  if (intOrLED) {
    intOrLED.reset();
    if (flashesAsStr.length > 1) {
      setTimeout(flashLEDs
        , (flashesAsStr.charAt(0) === flashesAsStr.charAt(1)) ? 270 : 420
        , null, flashesAsStr.substr(1)); } // off
  } else {
    if (flashesAsStr.length > 0) {
      (intOrLED = (flashesAsStr.charAt(0) === "R") ? LED1 : LED2).set();
      setTimeout(flashLEDs, 30, intOrLED, flashesAsStr); } // on
  }
}


// read temperature and display farenheit with flashes
function showTemp() {
  flashLEDs(Math.round(E.getTemperature() * 9 / 5 + 32));
}


// enter r() in console r() to run
var runningInterv = null;
function r() { // run
  if (!runningInterv) {
    showTemp();
    runningInterv = setInterval(showTemp, 10000); }
}

// enter s() in console to stop
function s() { // stop
  if (runningInterv) {
    runningInterv = clearInterval(runningInterv);
  }
}

// start automatically after saving the code
function onInit() {
  r();
}

...and this flashLEDs() works even better... I mean, is more frugal:

// show integers from 1 through 109 with red and green flashes:
// a red flash for each tens, and a green for each ones;
// example: flashLEDs(21); // flash red twice and green once
// Note: you cannot call it more often then about every 10 seconds
function flashLEDs(i, led) {
  if (led) {
    led.reset();
    if (i > 1) {
      setTimeout( flashLEDs
        , ((20 > i) && (i > 9)) ? 470 : 270
        , i - ((i > 9) ? 10 : 1) ); } // off
  } else {
    if (i > 0) {
      (led = (i > 9) ? LED1 : LED2).set();
      setTimeout(flashLEDs, 30, i, led); // on
    }
  }
}