If you have a <2007 Golf, your gateway is to old for the new rns510 models.
There are 2 options:
1) Buy a original B model rns510. Put firmware 1200 (or lower) on it and this way you don't have the battery drain. (firmwares 0900,1100,1200 are all original B version firmwares)
The problem is that with newer firmwares 1300,26xx,27xx,3xxx, etc. the 'vuci files' are changed and can't 'talk' with the older gateways. So the rns510 won't go in standby after a couple of minutes and draines the battery.
2) Buy and install a new gateway (you also need vagcom to program it).
Version 1k0907530 (1k0 907 530) of L revision or higher is required.
I bought a original RNS 510 B version two weeks ago, with fw1200, installed it, used vagcom to program things like the mfsw and cd-changer and everything works fine. My MKV GTI is from 06-2005 with the original (E version) gateway. No powerdrain...
There is also a 3rd option going to test it myself next week:
3) There are modified FW26xx and FW27xx files with the vuci code from 1200.
I've downloaded a modified FW2760 with 1200 vuci.
Found here:
http://vwnavi.com/showthread.php/13672-Unofficial-272x-software-and-SWL-recovery-CD/page24
So you DON'T NEED A NEW GATEWAY (only if you really want the newest firmware or you can't find a B model)