honestly it doesn't bother me. In practice it's more like 20 minutes, and if you haven't been using your phone, then you haven't been subjecting it to serious drain, and the number a battery live tile displays is usually within 0-3% of the actual value. If the tile says 68% but it's actually 65%, who cares? Perfect accuracy is not required; all you really need to know is, "am I closer to 60% or 70%?"
Admittedly if you've been playing a game or something, you could drop 30% in 20 minutes and the tile is useless, but it's a simple process of tapping the tile to get an updated value in the app. I KNOW that I have to check the app and not the tile after gaming, so it's not like im ever mislead by the tile: It's easy to know when it's wrong.