I wouldn't be that concerned even if the endurance isn't any better than the lower bound. A large, fast DIMM today would have 8GB of storage and 25 GB/s of bandwidth. If you write to the whole thing at full speed that'll get you a millennium of writing. If you're only ever writing to the smallest bit that won't be masked by a 8MB L3 then you've still got a year of continuous writing even in the absolute worst case.