I'm very aware that the VANOS system requires a perfect oil supply and that aged and hardened oil seals are bad news. The answer is to use exactly the quality of oil specified, change it every year and never let the level drop.
As far as Tarka is concerned, 19800 miles in 15 months would seem to be "regularly" and using the revs sensibly is also a good idea, so holding lower gears when having "fun" cannot do any harm!
So, all being well another 80,000 miles should be possible, but nothing is certain. The VANOS/Valvetronic system can be rebuilt, but it is wings off, if not engine out.
Fingers crossed!
