Hello @MagEBoard ,
Generally a browser should cache your preference to display 40 campaigns on the My Campaigns screen after you've selected it once. This should persist, even after logging out and back in.
If this isn't the case, there may be a caching error happening, which can be easily resolved by clearing cached files and images in your browser (not the history or saved passwords). Once the cache is cleared / reset, it should be able to save that preference once set.