Had a few GT TDI 170s and have always stuck to 4 years or 70k miles, better to be cautious given the consequences.
My approach to servicing might be considered a bit OTT but i normally do 25k miles a year so like to give the old girl some TLC
Every 6,000 miles - Oil (Castrol Edge FST 5/30) filter, air filter.
Every 12,000 miles - Oil change, replace all filters including fuel filter.
Every 18 months - brake fluid change.
As its not cost effective and worth the hassle to do the brake fluid change myself i take the Golf to my local Skoda dealership as they tend to be the cheapest at circa £60 including a courtesy car for the day. Apart form that i do my own servicing.