Question about creates/s and updates/s monitor stats

We are experimenting with increasing the expiration length of items in a large data set and monitoring the server stats as we go.

Most of them make sense (e.g. total no. of items and memory usage increase), but can anybody clarify why the create/s and update/s counts should grow significantly as the expiration increases? My gut instinct would be that the the actual number of create and updates would be unchanged.

Another (possibly) related thing is that the % of replica items is RAM seems to drop off rapidly from time to time.

Overall, there doesn't seem to be any drop off in performance.