Can you do some sort of a compromise based on how far away the due dates are? If there we’re mentioning timespans in seconds, then check every 10 seconds or so, but if we’re mentioning minutes, then check once a minute, hours for hours, etc.
I realize that due dates can change, but that’s not what I’m talking about here. I was actually thinking this could be completely client side javascript. It’s just the “Time until due” that would be changing.