Your friend is mistaken. He should've said, " Never buy a .375 because they will multiply like rabbits and are a gateway drug to larger bores." I started with one and now have three. I do not wish to mention the small expanse of time during which the acquisitions occured. What's worse is that I am now looking at larger bores.
It took the .325 WSM to revitalize the .323 bullet production in the US. With the 8x68 being so close to the .300 WM in performance and the latter being available in every gun shop, you're a unique fellow without the burden of others borrowing your ammunition.