My first a12 was held at 6000rpms for the best part of a day. It had no T/stat, and was stone cold.

IMO the less than perfect aspect of the A series would be,
The rod bolts as discussed
The stock cast pistons have the limitations that go with casties
The springs on the rockershaft need to be replaced with bushes. This imptoves lubrication, and prevents the rockers migrating resulting in bent push rods.
The PCD of the flywheel is too small.

aside from big ends bols breaking, I've never heard of the rods failing.