This must be a problem with the S54 engine since I have 2 E36 M3's with as many as 281K miles with zero VANOs issues. Consider the S52 engine is a single VANOs and hydraulic lifters with no valve adjustment required.
Failing VANOs seems to be the bolt issue not the actual VANOs. Replacing VANOs bolts to the cam is not that huge a maintenance effort and if I had one I would be pulling mine and upgrading the bolts.
I have rebuilt VANOs on S52s and it is an extremely simple system.
I wanted to replace my E36 M3 convertible with the E46 M3 and if I do I will certainly replace the bolts before driving it very much.
Good to know about this issue...