Yup, I'm with Mr Rubie on that. I recall that info in a post from Julian on the other channel a while back.
Lets see if we can't find it ;-)
Aha, here it is - quote/unquote from Mr Voelcker from TLOCUK
"The main BEB problem is down to the material used for the BEBs on the 12 valve engine only - the bearings were changed on the 24 valve and uses different material. Research suggests that is is down to an incompatibility with the oils and the bearing material - Japanese oils have higher levels of calcium which the bearings like, European oils have lower levels which leads to the problems, unless you look at some of the top end oils like Amsoil Synthetic, although the vehicle would need to run on this from birth.
Any BEB problems on 24valve engines appear to be down to machining issues or poor maintenace - there is no solid evidence to suggest that that there is a link between them."
So I presume that new shells from Mr 'Yota are the 24 valve shells that will not deteriorate over time if treated responsibly...