I've not experienced this myself, however from what I've read, I think over night might be sufficient to drain the battery without the updated gateway :(
I think the gateway is either stuffed behind the front wiper motor or up in the drivers side footwell somewhere...
Worth noting, aftermarket headunits don't need a new gateway.
![happy2 :happy2:](https://www.mk5golfgti.co.uk/forum/Smileys/newsmileys/happy2.gif)