My mistake not really a mistake, just lazy. It definately sounds like you should be offered a replacement. 4 hours and this wouldn't be worth a consideration when shopping around, I'd be mad. Who knows what is happening next week, but I imagine that they still have enough sp4 stock left to make haggling for an upgrade fruitless. Give it a go by all means if you're within warranty, but I doubt you'll get an sp5. I've only read of such replacement a few times but it was generally sp1 to an sp3.
I don't think we'll see an SP5 next week. At most, we might see an SP4 refresh with Kaby Lake. I hear you about haggling for an "upgrade," but I've found such things to be possible with Microsoft Stores when you have Microsoft Complete. Gotta catch a manager in the right mood, but it's been known to happen.
In any event, if Microsoft doesn't introduced anything new for the SP4, then I'll definitely be swapping out for a new one. This battery life just isn't cutting it.