Odd sleep light behaviour?

If I sleep my new mini the light pulses as it should and it wakes when I press a key on my wired keyboard. However I left it sleeping overnight and noticed power light was off not pulsing. Only way to wake it was to push power button on mini, it then woke from sleep, it hadn't shut down. This doesn't seem right to me, I've already had issues where my USB hub was causing it to shut off when I attempted to wake it, removing the hub cured that issue. I'm suspicious of this mini!