Hi There,
So, Great suggestion on dialing back the update frequency to save power! You are absolutely right that running frequent updates will drain the battery much faster. 
However, I did want to add a quick technical note regarding the display ghosting: it’s actually the partial refreshes that cause ghosting to build up over time. A full black-and-white refresh cycle is what the panel uses to clear out the residual charge (DC bias) 
and restore the capsules.
Manufacturers specifically advise forcing a full refresh to clear these artifacts. For example, Good Display’s E-paper Display FAQ states: “we suggest that after partial refresh for 5 times, it is necessary to add a black-and-white full screen refresh display… to improve ghosting.”
But your main point is spot on 
updating only when the CO2 shifts by 25–50 ppm is a much better approach for the longevity of the battery and the panel!
I have found this to be true with all the Seeed E-Papers I have tested and posted demo’s on. even though it’s a 6 year or more old tech, the controllers and panels are getting better and better. the 1.54" is great, seeed should offer it with a touch plane. 
HTH
GL 
PJ 
still waiting on the E1003 i won in live stream a while back. 