See posting about how to change the fluid. It is a sealed lifetime environment. Only question is, whose lifetime? VW generally defines lifetime as 100k miles.
Things to consider. Synthetic oil in a sealed environment will over time become contaminated with bits of metal warn from the gears. The filter will also start to fill up with little bits and pieces of stuff. The transmission generates a lot of heat, and the oil will break down if it gets hot enough.
Depends on you own personal level of paranoia. 50K miles seems like a reasonable length of time between changes. At least for me.
