Ben:
I have a high opinion of the third bite, and generally place a higher value on guns fitted with them.

Don't forget the Westley Richards C-bolt: on many early examples the single bite on the doll's head is the only fastener on the gun!

Most third bites have some slight camming action if well-fitted, Webley screw-grip is probably the best, but I like the Leonard-built Jeffery dolls-head with bite, and not just because I happen to own one! (Sadly, I dont own any DRs with screw-grips or WR C-bolts!)

A 'proper' third bite on a well-built rifle will definitely aid in longevity IMHO.