Bit flips aren't evenly distributed over time or across RAM. In other words, the vast, vast majority of DIMMs are good and will never have a bit flip. For those

Bit flips aren't evenly distributed over time or across RAM. In other words, the vast, vast majority of DIMMs are good and will never have a bit flip. For those modules, the money you spent on ECC will be in a sense "wasted". (Except for the value of knowing that you had a good module in the first place.)