I've owned a couple of VANOS equipped cars and I'm not sure if BMW has made updates since then, but I had one of the very common (and inexpensive) problems on my M5, which was the CPS sensors going bad (and there were 4 of them, all on the back of the heads, but, in BMW's defence, they weren't difficult to replace). These cars didn't suffer from VANOS seal/o-ring issues because the Sxx engines (///M cars) got Viton o-rings while the Mxx (non-M cars) got butyl rubber. As we know with BMW's valve covers, the butyl rubber gets hard, no longer flexes and then leaks. The same thing happens with the o-rings.
That said, my sister has had absolutely no issues with VANOS on her '03 330i, coming up on 300,000km now. The body will be long gone before it appears she'll have any mechanical issues with the engine.
But, from what I read at the time, the M62 guys were having o-ring issues (and chain issues, but that's another topic) while the S62 guys weren't, and this seems to be a "thing" with BMW, using butyl rubber for seals/gaskets that should be silicone or Viton, and you know they know that, because they'll use that material on the M-cars, lol.
Sooooo, there are some legitimate criticisms to be made about BMW's choice of materials with the VANOS systems, at least historically. Perhaps they've stopped using butyl rubber in more recent engines and this is no longer a problem?