Expansion tanks don't typically explode. More common failure mode is that they crack and start leaking. While a blade could come apart on a water pump, that doesn't happen often.Expansion tanks (typically) don't explode by themselves. Commonly this is caused by an external factor like the blade on the water pump coming apart.
I can't fault a person for wanting to take good care of their car, but you can go broke doing it if you replace every "weak point". If the cover is off and you don't mind spending the $70 bucks, than go for it. :thumbup:I don't know if the VANOS seals are leaky. But the VCG is and I've heard a lot about the VANOS issue. I just wonder if I should do the extra work while I have the valve cover off anyway. I doesn't look too hard but it is an extra $60-$70 ( I know, that's not too much). Plus there's a minor risk of breaking something, but I'm not too worried about that.