Just to add, it's not the quantity of rubber that matters, but the quality - the Original MGR bushes fitted at Longbridge frequently last many, many years and upwards of 80,000 miles and have large voids either side of the centre mount - picture borrowed from Dr Dave over on 'the other side' of an original but old / knackered bush -
And new MGR / XPart supplied bushes were similar when changed by Dave -
I'll also go digging to see when they changed the design, and see if we have any other complaints noted since then - but I don't believe we have.
The bushes are designed to have some 'flex' by design - both laterally and in a twisting motion.