Re: .30-378 Wby
On the throat erosion issue, you are correct that sustained fire will over heat the barrel and accelerate wear. However, it is also true that the more powder you burn in a given bore, the faster the erosion. Throat erosion would be visible after 500rds but still may not affect accuracy till later.
Barrel life is a subjective thing. For the 30-378, I would expect to get at least 1000rds of accurate fire before erosion starts to take effect. For the match shooter, this barrel life is quite low. For the average hunter, this would be several lifetimes.
Also the expected accuracy of a target shooter is much higher then a hunter. So even when a barrel is burnt out for a match shooter, it will be "lots" of life left for a hunter.
Enjoy your Accumark. My friend has one and it shoots very well also. When reading posts and opinions, always remember the point of view of the writer and their expectations.